Mold for injecting molding preforms

ABSTRACT

This invention relates to methods and apparatus for making articles made of polyester, preferably polyethylene terephthalate (PET), having coated directly to at least one of the surfaces thereof one or more layers of thermoplastic material with good gas-barrier characteristics. In one preferred method and apparatus, preforms are injection molded, barrier-coated immediately thereafter, and remain on a mold portion for a time to speed cooling of the completed preform. Preferably the barrier-coated articles take the form of preforms coated by at least one layer of barrier material and the containers are blow-molded therefrom. Such barrier-coated containers are preferably of the type to hold beverages such as soft drinks, beer or juice. The preferred barrier materials have a lower permeability to oxygen and carbon dioxide than PET as well as key physical properties similar to PET. The materials and methods provide that the barrier layers have good adherence to PET, even during and after the blow molding process to form containers from preforms. Preferred barrier coating materials include poly(hydroxyamino ethers).

RELATED APPLICATION DATA

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/788,905, filed Feb. 26, 2004, which is a continuation ofU.S. patent application Ser. No. 10/090,471, filed Mar. 4, 2002 and nowissued as U.S. Pat. No. 6,939,591, which is a divisional of U.S. patentapplication Ser. No. 09/296,695, filed Apr. 21, 1999 and now issued asU.S. Pat. No. 6,352,426, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/174,971, filed Oct. 19, 1998 and now issued asU.S. Pat. No. 6,391,408, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/953,595, filed Oct. 17, 1997 and now issued asU.S. Pat. No. 6,312,641, and also claims priority under 35 U.S.C.§119(e) from U.S. Provisional Application No. 60/078,641, filed Mar. 19,1998.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus and method for makingbarrier-coated polyesters, preferably barrier coated polyethyleneterephthalate (PET) and articles made therefrom. Preferably thebarrier-coated PET takes the form of preforms having at least one layerof a barrier material and the bottles blow-molded therefrom.

The use of plastic containers as a replacement for glass or metalcontainers in the packaging of beverages has become increasinglypopular. The advantages of plastic packaging include lighter weight,decreased breakage as compared to glass, and potentially lower costs.The most common plastic used in making beverage containers today is PET.Virgin PET has been approved by the FDA for use in contact withfoodstuffs. Containers made of PET are transparent, thin-walled,lightweight, and have the ability to maintain their shape bywithstanding the force exerted on the walls of the container bypressurized contents, such as carbonated beverages. PET resins are alsofairly inexpensive and easy to process.

Despite these advantages and its widespread use, there is a seriousdownside to the use of PET in thin-walled beverage containers:permeability to gases such as carbon dioxide and oxygen. These problemsare of particular importance when the bottle is small. In a smallbottle, the ratio of surface area to volume is large which allows for alarge surface for the gas contained within to diffuse through the wallsof the bottle. The permeability of PET bottles results in soft drinksthat go “flat” due to the egress of carbon dioxide, as well as beveragesthat have their flavor spoiled due to the ingress of oxygen. Because ofthese problems, PET bottles are not suitable for all uses desired byindustry, and for many of the existing uses, the shelf-life of liquidspackaged in PET bottles is shorter than desired.

U.S. Pat. No. 5,464,106 to Slat, et al, describes bottles formed fromthe blow molding of preforms having a barrier layer. The barriermaterials disclosed are polyethylene naphthalate, saran, ethylene vinylalcohol copolymers or acrylonitrile copolymers. In Slat's technique, thebarrier material and the material to form the inner wall of the preformare coextruded in the shape of a tube. This tube is then cut intolengths corresponding to the length of the preform, and is then placedinside a mold wherein the outer layer of the preform is injected overthe tube to form the finished preform. The preform may then beblow-molded to form a bottle. The drawbacks of this method are that mostof the barrier materials disclosed do not adhere well to PET, and thatthe process itself is rather cumbersome.

A family of materials with good barrier characteristics are thosedisclosed in U.S. Pat. No. 4,578,295 to Jabarin. Such barrier materialsinclude copolymers of terephthalic acid and isophthalic acid withethylene glycol and at least one diol. This type of material iscommercially available as B-010 from Mitsui Petrochemical Ind. Ltd.(Japan). These barrier materials are miscible with polyethyleneterephthalate and form blends of 80-90% PET and 10-20% of thecopolyester from which barrier containers are formed. The containersmade from these blends are about 20-40% better gas barriers to CO2transmission than PET alone. Although some have claimed that thispolyester adheres to PET without delamination, the only preforms orcontainers disclosed were made with blends of these materials.

Another group of materials, the polyamine-polyepoxides, have beenproposed for use as a gas-barrier coating. These materials can be usedto form a barrier coating on polypropylene or surface-treated PET, asdescribed in U.S. Pat. No. 5,489,455 to Nugent, Jr. et al. Thesematerials commonly come as a solvent or aqueous based thermosettingcomposition and are generally spray coated onto a container and thenheat-cured to form the finished barrier coating. Being thermosets, thesematerials are not conducive to use as preform coatings, because once thecoating has been cured, it can no longer be softened by heating and thuscannot be blow molded, as opposed to thermoplastic materials which canbe softened at any time after application.

Another type of barrier-coating, that disclosed in U.S. Pat. No.5,472,753 to Farha, relies upon the use of a copolyester to effectadherence between PET and the barrier material. Farha describes twotypes of laminates, a three-ply and a two-ply. In the three-plylaminate, an amorphous, thermoplastic copolyester is placed between thebarrier layer of phenoxy-type thermoplastic and the layer of PET toserve as a tie layer to bind the inner and outer layers. In the two-plylaminate, the phenoxy-type thermoplastic is first blended with theamorphous, thermoplastic copolyester and this blend is then applied tothe PET to form a barrier. These laminates are made either by extrusionor by injection molding wherein each layer is allowed to cool before theother layer of material is injected.

PCT Application No. PCT/US95/17011, to Collette et al., which waspublished on Jul. 4, 1996, describes a method of cooling multilayerpreforms. The disclosed apparatus comprises a rotary turret havingmultiple faces, each face carrying an array of cores. The cores areinserted into corresponding mold cavities. Multiple melt streams arebrought together and coinjected into each cavity to form a multilayerpreform on each core. After the preform is injected, the cores areremoved from the cavities and the turret is rotated, presenting a newset of cores to the mold cavities. The just-injected cavities remain onthe cores cooling while preforms are formed on other arrays of cores.The drawbacks of the Collette application include that coinjectionresults in preforms that are inconsistent and have unpredictablelayering. Thus, distribution of barrier materials in such a preformwould be unpredictable and would result in a preform having unreliablebarrier properties.

Since PET containers can be manufactured by injection molding using onlya single injection of PET, manufacture is relatively easy and productioncycle time is low. Thus, PET containers are inexpensive. Even if knownbarrier materials can be bonded to PET to create a saleable containerwith reliable barrier properties, methods and apparatus for making suchcontainers within a competitive cycle time and cost have not beendevised. Production cycle time is especially important because a lowercycle time enables a manufacturer to make more efficient use of itscapital equipment. Thus, low cycle time enables higher volume and lessexpensive production of containers. Cost-effective production would benecessary to develop a viable alternative to monolayer PET containers.

Thus, the need exists for an apparatus and method for makingbarrier-coated PET preforms and containers which are economical,cosmetically appealing, easy to produce, and have good barrier andphysical properties remains unfulfilled.

SUMMARY OF THE INVENTION

This invention relates to methods and apparatus for making PET articleshaving coated upon the surfaces thereof one or more thin layers ofthermoplastic material with good gas-barrier characteristics. Thearticles of the present invention are preferably in the form of preformsand containers.

In an aspect of the present invention there is provided a barrier coatedpreform comprising a polyester layer and a barrier layer comprisingbarrier material, wherein the polyester layer is thinner in the end capthan in the wall portion and the barrier layer is thicker in the end capthan in the wall portion.

In another aspect of the present invention there is provided a methodfor making a barrier coated polyester article. A polyester article withat least an inner surface and an outer surface is formed by injectingmolten polyester through a first gate into the space defined by a firstmold half and a core mold half, where the first mold half and the coremold half are cooled by circulating fluid and the first mold halfcontacts the outer polyester surface and the core mold half contacts theinner polyester surface. Following this, the molten polyester is allowedto remain in contact with the mold halves until a skin forms on theinner and outer polyester surfaces which surrounds a core of moltenpolyester. The first mold half is then removed from the polyesterarticle, and the skin on the outer polyester surface is softened by heattransfer from the core of molten polyester, while the inner polyestersurface is cooled by continued contact with the core mold half. Thepolyester article, still on the core mold half is then placed into asecond mold half, wherein the second mold half is cooled by circulatingfluid. In the coating step, the barrier layer comprising barriermaterial is placed on the outer polyester surface by injecting moltenbarrier material through a second gate into the space defined by thesecond mold half and the outer polyester surface to form the barriercoated polyester article. The second mold half is then removed from thebarrier coated article and then the barrier coated article is removedfrom the core mold half. The barrier materials used in the processpreferably comprise a Copolyester Barrier Materials, Phenoxy-typeThermoplastics, Polyamides, polyethylene naphthalate, polyethylenenaphthalate copolymers, polyethylene naphthalate/polyethyleneterephthalate blends, and combinations thereof.

In a further aspect of the present invention, there is provided a methodof making and coating preforms. The method begins by closing a moldcomprising a stationary half and a movable half, wherein the stationarymold half comprises at least one preform molding cavity and at least onepreform coating cavity and the movable mold half comprises a rotatableplate having mounted thereon a number of mandrels equal to the sum ofthe number of preform molding cavities and preform coating cavities. Theremaining steps comprise: injecting a first material into the spacedefined by a mandrel and a preform molding cavity to form a preformhaving an inner surface and an outer surface; opening the mold; rotatingthe rotatable plate; closing the mold; injecting a second material intothe space defined by the outer surface of the preform and the preformcoating cavity to form a coated preform; opening the mold; removing thecoated preform.

In accordance with a preferred embodiment having features in accordancewith the present invention, an apparatus for injection moldingmultilayer preforms is provided. The apparatus comprises first andsecond mold cavities in communication with first and second meltsources, respectively. A turntable is provided and is divided into aplurality of stations, with at least one mold core disposed on eachstation. The turntable is adapted to rotate each station to a firstposition at which a core on the station interacts with the first moldcavity to form a first preform layer, then to a second position at whichthe core interacts with the second mold cavity to form a second preformlayer. Finally, the turntable is further adapted to rotate the stationto at least one cooling position, at which the molded preform remains onthe core to cool.

In accordance with another preferred embodiment having features inaccordance with the present invention, a mold apparatus for injectionmolding multilayer preforms is provided. The mold apparatus has a firstmold body which is adapted to fit about a mold core to define a firstlayer cavity therebetween, a first gate area, and is in communicationwith a first melt source. A second mold body is adapted to fit about afirst preform layer disposed on the mold core to define a second layercavity therebetween, has a second gate area, and is in communicationwith a second melt source. At least one of the gate areas has Ampcoloymetal inserts disposed therein.

In accordance with another preferred embodiment having features inaccordance with the present invention, a mold apparatus for injectionmolding multilayer preforms is provided. The mold apparatus has a firstmold body which is adapted to fit about a mold core, defining a firstlayer cavity therebetween. The first layer cavity has a base end and amain body. The first mold body is in communication with a first meltsource and has a first gate area adjacent the base end of the firstlayer cavity. A thickness of the cavity at the base end is less than thethickness of the main body of the cavity the mold apparatus also has asecond mold body, which is adapted to fit about a first preform layerdisposed on the mold core, defining a second layer cavity therebetween.The second mold body is in communication with a second melt source andhas a second gate area.

In accordance with yet another preferred embodiment having features inaccordance with the present invention, a mold for injection moldingmultilayer preforms is provided. The mold has a mandrel and first andsecond cavities. The mandrel is hollow and has a wall of substantiallyuniform thickness. A coolant supply tube is disposed centrally withinthe hollow mandrel to supply coolant directly to a base end of themandrel. The first cavity has a gate for injecting molten plastic. Agate area of the cavity has an insert of material having greater heattransfer properties than the majority of the cavity.

In accordance with a further preferred embodiment having features inaccordance with the present invention, a method for improving injectionmold performance is provided. The method includes forming an opening ina wall of a mold cavity. The opening is sized and adapted so that moltenplastic will not substantially enter the opening. A passageway is formedconnecting the opening to a source of air pressure. The method furtherincludes providing a valve between the opening and the source of airpressure.

In accordance with another preferred embodiment having features inaccordance with the present invention, a method for injection moldingand cooling a multilayer preform is provided. The method includes thesteps of providing a mold core disposed on a turntable and having aninternal cooling system, rotating the turntable so that the core isaligned with a first mold cavity, engaging the core with the first moldcavity, and injecting a melt to form a first preform layer. The firstpreform layer is held within the mold cavity to cool until a skin isformed on a surface of the layer, but an interior of the layer remainssubstantially molten. The core is then removed from the first moldcavity while retaining the molded preform layer on the core and theturntable is rotated so that the core is aligned with a second moldcavity. The core is engaged with the second mold cavity and a melt isinjected to form a second preform layer on top of the first preformlayer. The core is removed from the second mold cavity while retainingthe molded preform on the core and the turntable is rotated so that thecore and preform are in a cooling position during which the preformcools upon the core. The preform is eventually removed from the core.

In accordance with one aspect of the present invention, there isprovided a laminate comprising at least one layer of polyethyleneterephthalate directly adhered to at least one layer of barriermaterial. The polyethylene terephthalate has an isophthalic acid contentof at least about 2% by weight. Barrier materials used includeCopolyester Barrier Materials, Phenoxy-type Thermoplastics, Polyamides,polyethylene naphthalate, polyethylene naphthalate copolymers,polyethylene naphthalate/polyethylene terephthalate blends, andcombinations thereof. In preferred embodiments, the laminate is providedin the form of preforms and containers.

In accordance with a further aspect of the present invention, there isprovided a preform comprising at least two layers, wherein the firstlayer is thinner in the end cap than in the wall portion and the secondlayer is thicker in the end cap than in the wall portion. The firstlayer comprises polyethylene terephthalate having an isophthalic acidcontent of at least about 2% by weight and the second layer comprises abarrier material. Barrier materials used include Copolyester BarrierMaterials, Phenoxy-type Thermoplastics, Polyamides, polyethylenenaphthalate, polyethylene naphthalate copolymers, polyethylenenaphthalate/polyethylen-e terephthalate blends, and combinationsthereof.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described hereinabove. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an uncoated preform as is used as a starting material forembodiments of the present invention.

FIG. 2 is a cross-section of a preferred uncoated preform of the typethat is barrier-coated in accordance with an embodiment the presentinvention.

FIG. 3 is a cross-section of one preferred embodiment of barrier-coatedpreform of the present invention.

FIG. 4 is a cross-section of another preferred embodiment of abarrier-coated preform of an embodiment of the present invention.

FIG. 4A is an enlargement of a section of the wall portion of a preformsuch as that made by a LIM-over-inject process. Not all preforms of thetype in FIG. 4 made in accordance with an embodiment of the presentinvention will have this type of layer arrangement.

FIG. 5 is a cross-section of another embodiment of a barrier-coatedpreform of an embodiment of the present invention.

FIG. 6 is a cross-section of a preferred preform in the cavity of ablow-molding apparatus of a type that may be used to make a preferredbarrier-coated container of an embodiment of the present invention.

FIG. 7 is one preferred embodiment of barrier-coated container of thepresent invention.

FIG. 8 is a cross-section of one preferred embodiment of abarrier-coated container having features in accordance with the presentinvention.

FIG. 9 is a cross-section of an injection mold of a type that may beused to make a preferred barrier-coated preform in accordance with thepresent invention.

FIGS. 10 and 11 are two halves of a molding machine to makebarrier-coated preforms.

FIGS. 12 and 13 are two halves of a molding machine to make forty-eighttwo-layer preforms.

FIG. 14 is a perspective view of a schematic of a mold with mandrelspartially located within the molding cavities.

FIG. 15 is a perspective view of a mold with mandrels fully withdrawnfrom the molding cavities, prior to rotation.

FIG. 16 is a three-layer embodiment of a preform.

FIG. 17 is a front view of a preferred embodiment of an apparatus formaking preforms in accordance with the present invention;

FIG. 18 is a cross-section of the apparatus of FIG. 17 taken along lines18-18;

FIG. 19 is a chart showing the relative positions of stations of theapparatus of FIG. 17 during a production cycle;

FIG. 20 is a front view of another preferred embodiment of an apparatusfor making preforms in accordance with the present invention;

FIG. 21 is a close up view of a station and actuator of the apparatus ofFIG. 20;

FIG. 22 is a front view of another preferred embodiment of an apparatusfor making preforms in accordance with the present invention;

FIG. 23 is a front view of the apparatus of FIG. 22 in a closedposition;

FIG. 24 is a chart showing the relative positions of stations of theapparatus of FIG. 22 during a production cycle;

FIG. 25 is a schematic of a lamellar injection molding (LIM) system.

FIG. 26 is a cross-section of an injection mold of a type that may beused to make a preferred preform of the present invention;

FIG. 27 is a cross-section of the mold of FIG. 26 taken along lines27-27;

FIG. 28 is a cutaway close up view of the area of FIG. 26 defined byline 28.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A. General Descriptionof the Invention

This invention relates to methods and apparatus for making plasticarticles having coatings comprising one or more layers of thermoplasticmaterial with good gas-barrier characteristics. As presentlycontemplated, one embodiment of barrier coated article is a bottle ofthe type used for beverages. Alternatively, embodiments of the barriercoated articles of the present invention could take the form of jars,tubs, trays, or bottles for holding liquid foods. However, for the sakeof simplicity, these embodiments will be described herein primarily inthe context of beverage bottles and the preforms from which they aremade by blow-molding.

Furthermore, the invention is described herein specifically in relationto polyethylene terephthalate (PET) but it is applicable to many otherthermoplastics of the polyester type. Examples of such other materialsinclude polyethylene 2,6- and 1,5-naphthalate (PEN), PETG,polytetramethylene 1,2-dioxybenzoate and copolymers of ethyleneterephthalate and ethylene isophthalate.

In especially preferred embodiments, “high IPA PET” is used as thepolyester which is barrier coated. As it is used herein, the term“high-IPA PET” refers to PET to which IPA was added during tomanufacture to form a copolymer in which the IPA content is more thanabout 2% by weight, preferably 2-10% IPA by weight, more preferably3-8%, most preferably about 4-5% IPA by weight. The most preferred rangeis based upon current FDA regulations, which do not allow for PETmaterials having an IPA content of more than 5% to be in contact withfood or drink. If such regulations are not a concern, then an IPAcontent of 5-10% is preferred. As used herein, “PET” includes “high IPAPET.”

The high-IPA PET (more than about 2% by weight) is preferred because theinventor has surprisingly discovered that use of high-IPA PET in theprocesses for making barrier preforms and containers, provides forbetter interlayer adhesion than is found in those laminates comprisingPET with no IPA or low IPA. Additionally, it has been found thatinterlayer adhesion improves as the IPA content rises. Incorporation ofthe higher amounts of IPA into the PET results in a decrease in the rateof crystallization of the high IPA PET material as compared to PEThomopolymer, or PET having lower amounts of IPA. The decrease in therate of crystallization allows for the production of PET layers (made ofhigh IPA PET) having a lower level of crystallinity than what isachieved with low-IPA PET or homopolymer PET when they are made intobarrier preforms by similar procedures. The lower crystallinity of thehigh-IPA PET is important in reducing crystallinity at the surface ofthe PET, i.e. the interface between the PET and the barrier material.Lower crystallinity allows for better adhesion between the layers andalso provides for a more transparent container following blow molding ofthe preform.

Preferably, the preforms and containers have the barrier coatingdisposed on their outer surfaces or within the wall of the container. Incontrast with the technique of Slat, which produces multilayeredpreforms in which the layers are readily separated, in embodiments ofthe present invention the thermoplastic barrier material adheresdirectly and strongly to the PET surface and is not easily separatedtherefrom. Adhesion between the layers results without the use of anyadditional materials such as an adhesive material or a tie layer. Thecoated preforms are processed, preferably by stretch blow molding toform bottles using methods and conditions similar to those used foruncoated PET preforms. The containers which result are strong, resistantto creep, and cosmetically appealing as well as having good gas-barrierproperties.

One or more layers of a barrier material are employed in carrying outthe present invention. As used herein, the terms “barrier material”,“barrier resin” and the like refer to materials which, when used to formarticles, preferably have key physical properties similar to PET, adherewell to PET, and have a lower permeability to oxygen and carbon dioxidethan PET.

Once a suitable barrier material is chosen, an apparatus and method foreconomically manufacturing a container using the barrier material isnecessary. One important method and apparatus involves using aninjection molding machine in conjunction with a mold comprising amandrel or core and a cavity. A first layer of a preform is moldedbetween the mandrel and a first cavity of the mold when a moltenpolyester is injected therein. The first layer remains on the mandrelwhen the mandrel is pulled out of the cavity, moved, and inserted into asecond mold cavity. A second layer of the material, preferably a barrierlayer or a layer comprising barrier material, is then injected over theexisting first preform layer. The mandrel and accompanying preform arethen removed from the second cavity and a robot removes the preform fromthe mandrel. While the robot cools the molded preform, the mandrel isavailable for another molding cycle.

In another embodiment, the apparatus retains the preform on the mandrelafter removal from the second mold cavity but indexes the mandrel out ofthe way of the mold cavities in order to cool the new preform. Duringthis time, other mandrels of the apparatus interact with the moldcavities to form preform layers. After the preform is sufficientlycooled, it is removed from the mandrel by a robot or other device andthe mandrel is available to start the process over again. This methodand apparatus allows preforms to be cooled on the mandrel withoutsubstantially increasing cycle time.

A number of barrier materials having the requisite low permeability togases such as oxygen and carbon dioxide are useful in embodiments of thepresent invention, the choice of barrier material being partly dependentupon the mode or application as described below. Preferred barriermaterials for use in barrier coatings fall into two major categories:(1) copolyesters of terephthalic acid, isophthalic acid, and at leastone diol having good barrier properties as compared to PET, such asthose disclosed in U.S. Pat. No. 4,578,295 to Jabarin, and which iscommercially available as B-010 (Mitsui Petrochemical Ind. Ltd., Japan);and (2) hydroxy-functional poly(amide-ethers) such as those described inU.S. Pat. Nos. 5,089,588 and 5,143,998, poly(hydroxy amide ethers) suchas those described in U.S. Pat. No. 5,134,218, polyethers such as thosedescribed in U.S. Pat. Nos. 5,115,075 and 5,218,075, hydroxy-functionalpolyethers such as those as described in U.S. Pat. No. 5,164,472,hydroxy-functional poly(ether sulfonamides) such as those described inU.S. Pat. No. 5,149,768, poly(hydroxy ester ethers) such as thosedescribed in U.S. Pat. No. 5,171,820, hydroxy-phenoxyether polymers suchas those described in U.S. Pat. No. 5,814,373, and poly(hydroxyaminoethers) (“PHAE”) such as those described in U.S. Pat. No. 5,275,853. Thebarrier materials described in (1) above are referred to herein by theterm “Copolyester Barrier Materials”. The compounds described in thepatents in (2) above are collectively categorized and referred to hereinby the term “Phenoxy-type Thermoplastic” materials. All the patentsreferenced in this paragraph are hereby incorporated in their entiretiesinto this disclosure by this reference thereto.

Preferred Copolyester Barrier Materials will have FDA approval. FDAapproval allows for these materials to be used in containers where theyare in contact with beverages and the like which are intended for humanconsumption. To the inventor's knowledge, none of the Phenoxy-typeThermoplastics have FDA approval as of the date of this disclosure.Thus, these materials are preferably used in multi-layered containers inlocations which do not directly contact the contents, if the contentsare ingestible.

In carrying out preferred methods of the present invention to formbarrier coated preforms and bottles, an initial preform is coated withat least one additional layer of material comprising barrier material,polyesters such as PET, post-consumer or recycled PET (collectivelyrecycled PET), and/or other compatible thermoplastic materials. Acoating layer may comprise a single material, a mix or blend ofmaterials (heterogeneous or homogeneous), an interwoven matrix of two ormore materials, or a plurality of microlayers (lamellae) comprised of atleast two different materials. In one embodiment, the initial preformcomprises a plurality of microlayers, such as may be prepared by alamellar injection molding process. Initial preforms comprise polyester,and it is especially preferred that initial preforms comprise virginmaterials which are approved by the FDA for being in contact withfoodstuffs.

Thus the preforms and containers of embodiments of the present inventionmay exist in several embodiments, such as: virgin PET coated with alayer of barrier material; virgin PET coated with a layer of materialcomprising alternating microlayers of barrier material and recycled PET;virgin PET coated with a barrier layer which is in turn coated withrecycled PET; microlayers of virgin PET and a barrier material coatedwith a layer of recycled PET; or virgin PET coated with recycled PETwhich is then coated with barrier material. In any case, at least onelayer must comprise at least one barrier material.

As described previously, preferred barrier materials for use inaccordance with the present invention are Copolyester Barrier Materialsand Phenoxy-type Thermoplastics. Other barrier materials having similarproperties may be used in lieu of these barrier materials. For example,the barrier material may take the form of other thermoplastic polymers,such as acrylic resins including polyacrylonitrile polymers,acrylonitrile styrene copolymers, polyamides, polyethylene naphthalate(PEN), PEN copolymers, and PET/PEN blends. Preferred barrier materialsin accordance with embodiments of the present invention have oxygen andcarbon dioxide permeabilities which are less than one-third those ofpolyethylene terephthalate. For example, the Copolyester BarrierMaterials of the type disclosed in the aforementioned patent to Jabarinwill exhibit a permeability to oxygen of about 11 cc mil/100 in² day anda permeability to carbon dioxide of about 2 cc mil/100 in² day. Forcertain PHAEs, the permeability to oxygen is less than 1 cc mil/100 in²day and the permeability to carbon dioxide is 3.9 cc mil/100 in² day.The corresponding CO₂ permeability of polyethylene terephthalate,whether in the recycled or virgin form, is about 12-20 cc mil/100 in²day.

The methods of embodiments of the present invention provide for acoating to be placed on a preform which is later blown into a bottle.Such methods are preferable to placing coatings on the bottlesthemselves. Preforms are smaller in size and of a more regular shapethan the containers blown therefrom, making it simpler to obtain an evenand regular coating. Furthermore, bottles and containers of varyingshapes and sizes can be made from preforms of similar size and shape.Thus, the same equipment and processing can be used to produce preformsto form several different kinds of containers. The blow-molding may takeplace soon after molding, or preforms may be made and stored for laterblow-molding. If the preforms are stored prior to blow-molding, theirsmaller size allows them to take up less space in storage.

Even though it is preferable to form containers from coated preforms asopposed to coating containers themselves, they have generally not beenused because of the difficulties involved in making containers fromcoated or multi-layer preforms. One step where the greatest difficultiesarise is during the blow-molding process to form the container from thepreform. During this process, defects such as delamination of thelayers, cracking or crazing of the coating, uneven coating thickness,and discontinuous coating or voids can result. These difficulties can beovercome by using suitable barrier materials and coating the preforms ina manner that allows for good adhesion between the layers.

Thus, one aspect of the present invention is the choice of a suitablebarrier material. When a suitable barrier material is used, the coatingsticks directly to the preform without any significant delamination, andwill continue to stick as the preform is blow-molded into a bottle andafterwards. Use of a suitable barrier material also helps to decreasethe incidence of cosmetic and structural defects which can result fromblow-molding containers as described above.

It should be noted that although most of the discussion, drawings, andexamples of making coated preforms deal with two layer preforms, suchdiscussion is not intended to limit the present invention to two layerarticles. The two layer barrier containers and preforms of the presentinvention are suitable for many uses and are cost-effective because ofthe economy of materials and processing steps. However, in somecircumstances and for some applications, preforms consisting of morethan two layers may be desired. Use of three or more layers allows forincorporation of materials such as recycled PET, which is generally lessexpensive than virgin PET or the preferred barrier materials. Thus, itis contemplated as part of the present invention that all of the methodsfor producing the barrier-coated preforms of the present invention whichare disclosed herein and all other suitable methods for making suchpreforms may be used, either alone or in combination to producebarrier-coated preforms and containers comprised of two or more layers.

B. Detailed Description of the Drawings

Referring to FIG. 1, a preferred uncoated preform 30 is depicted. Thepreform is preferably made of an FDA approved material such as virginPET and can be of any of a wide variety of shapes and sizes. The preformshown in FIG. 1 is of the type which will form a 16 oz. carbonatedbeverage bottle that requires an oxygen and carbon dioxide barrier, butas will be understood by those skilled in the art, other preformconfigurations can be used depending upon the desired configuration,characteristics and use of the final article. The uncoated preform 30may be made by injection molding as is known in the art or by methodsdisclosed herein.

Referring to FIG. 2, a cross-section of the preferred uncoated preform30 of FIG. 1 is depicted. The uncoated preform 30 has a neck portion 32and a body portion 34. The neck portion 32 begins at the opening 36 tothe interior of the preform 30 and extends to and includes the supportring 38. The neck portion 32 is further characterized by the presence ofthe threads 40, which provide a way to fasten a cap for the bottleproduced from the preform 30. The body portion 34 is an elongated andcylindrically shaped structure extending down from the neck portion 32and culminating in the rounded end cap 42. The preform thickness 44 willdepend upon the overall length of the preform 30 and the wall thicknessand overall size of the resulting container.

Referring to FIG. 3, a cross-section of one type of barrier-coatedpreform 50 having features in accordance with the present invention isdisclosed. The barrier-coated preform 50 has a neck portion 32 and abody portion 34 as in the uncoated preform 30 in FIGS. 1 and 2. Thebarrier coating layer 52 is disposed about the entire surface of thebody portion 34, terminating at the bottom of the support ring 38. Abarrier coating layer 52 in the embodiment shown in the figure does notextend to the neck portion 32, nor is it present on the interior surface54 of the preform which is preferably made of an FDA approved materialsuch as PET. The barrier coating layer 52 may comprise either a singlematerial or several microlayers of at least two materials. The overallthickness 56 of the preform is equal to the thickness of the initialpreform plus the thickness 58 of the barrier layer, and is dependentupon the overall size and desired coating thickness of the resultingcontainer. By way of example, the wall of the bottom portion of thepreform may have a thickness of 3.2 millimeters; the wall of the neckfinish, a cross-sectional dimension of about 3 millimeters; and thebarrier material applied to a thickness of about 0.3 millimeters.

Referring to FIG. 4, a preferred embodiment of a coated preform 60 isshown in cross-section. The primary difference between the coatedpreform 60 and the coated preform 50 in FIG. 3 is the relative thicknessof the two layers in the area of the end cap 42. In coated preform 50,the barrier layer 52 is generally thinner than the thickness of theinitial preform throughout the entire body portion of the preform. Incoated preform 60, however, the barrier coating layer 52 is thicker at62 near the end cap 42 than it is at 64 in the wall portion 66, andconversely, the thickness of the inner polyester layer is greater at 68in the wall portion 66 than it is at 70, in the region of the end cap42. This preform design is especially useful when the barrier coating isapplied to the initial preform in an overmolding process to make thecoated preform, as described below, where it presents certain advantagesincluding that relating to reducing molding cycle time. These advantageswill be discussed in more detail below. The barrier coating layer 52 maybe homogeneous or it may be comprised of a plurality of microlayers.

FIG. 4A is an enlargement of a wall section of the preform showing themakeup of the layers in a LIM-over-inject embodiment of preform. The LIMprocess will be discussed in more detail below. The layer 72 is theinner layer of the preform and 74 is the outer layer of the preform. Theouter layer 74 comprises a plurality of microlayers of material as willbe made when a LIM system is used. Not all preforms of FIG. 4 will be ofthis type.

Referring to FIG. 5, another embodiment of a coated preform 76 is shownin cross-section. The primary difference between the coated preform 76and the coated preforms 50 and 60 in FIGS. 3 and 4, respectively, isthat the barrier coating layer 52 is disposed on the neck portion 32 aswell as the body portion 34.

The barrier preforms and containers can have layers which have a widevariety of relative thicknesses. In view of the present disclosure, thethickness of a given layer and of the overall preform or container,whether at a given point or over the entire container, can be chosen tofit a coating process or a particular end use for the container.Furthermore, as discussed above in regard to the barrier coating layerin FIG. 3, the barrier coating layer in the preform and containerembodiments disclosed herein may comprise a single material or severalmicrolayers of two or more materials.

After a barrier-coated preform, such as that depicted in FIG. 3, isprepared by a method and apparatus such as those discussed in detailbelow, it is subjected to a stretch blow-molding process. Referring toFIG. 6, in this process a barrier-coated preform 50 is placed in a mold80 having a cavity corresponding to the desired container shape. Thebarrier-coated preform is then heated and expanded by stretching and byair forced into the interior of the preform 50 to fill the cavity withinthe mold 80, creating a barrier-coated container 82. The blow moldingoperation normally is restricted to the body portion 34 of the preformwith the neck portion 32 including the threads, pilfer ring, and supportring retaining the original configuration as in the preform.

Referring to FIG. 7, there is disclosed an embodiment of barrier coatedcontainer 82 in accordance with the present invention, such as thatwhich might be made from blow molding the barrier coated preform 50 ofFIG. 3. The container 82 has a neck portion 32 and a body portion 34corresponding to the neck and body portions of the barrier-coatedpreform 50 of FIG. 3. The neck portion 32 is further characterized bythe presence of the threads 40 which provide a way to fasten a cap ontothe container.

When the barrier-coated container 82 is viewed in cross-section, as inFIG. 8, the construction can be seen. The barrier coating 84 covers theexterior of the entire body portion 34 of the container 82, stoppingjust below the support ring 38. The interior surface 86 of thecontainer, which is made of an FDA-approved material, preferably PET,remains uncoated so that only the interior surface 86 is in contact withbeverages or foodstuffs. In one preferred embodiment that is used as acarbonated beverage container, the thickness 87 of the barrier coatingis preferably 0.020-0.060 inch, more preferably 0.030-0.040 inch; thethickness 88 of the PET layer is preferably 0.080-0.160 inch, morepreferably 0.100-0.140 inch; and the overall wall thickness 90 of thebarrier-coated container 82 is preferably 0.140-0.180 inch, morepreferably 0.150-0.170 inch. Preferably, on average, the overall wallthickness 90 of the container 82 derives the majority of its thicknessfrom the inner PET layer.

FIG. 9 illustrates a preferred type of mold for use in methods whichutilize overmolding. The mold comprises two halves, a cavity half 92 anda mandrel half 94. The cavity half 92 comprises a cavity in which anuncoated preform is placed. The preform is held in place between themandrel half 94, which exerts pressure on the top of the preform and theledge 96 of the cavity half 92 on which the support ring 38 rests. Theneck portion 32 of the preform is thus sealed off from the body portionof the preform. Inside the preform is the mandrel 98. As the preformsits in the mold, the body portion of the preform is completelysurrounded by a void space 100. The preform, thus positioned, acts as aninterior die mandrel in the subsequent injection procedure, in which themelt of the overmolding material is injected through the gate 102 intothe void space 100 to form the coating. The melt, as well as theuncoated preform, is cooled by fluid circulating within channels 104 and106 in the two halves of the mold. Preferably the circulation inchannels 104 is completely separate from the circulation in the channels106.

FIGS. 10 and 11 are a schematic of a portion of the preferred type ofapparatus to make coated preforms in accordance with the presentinvention. The apparatus is an injection molding system designed to makeone or more uncoated preforms and subsequently coat the newly-madepreforms by over-injection of a barrier material. FIGS. 10 and 11illustrate the two halves of the mold portion of the apparatus whichwill be in opposition in the molding machine. The alignment pegs 110 inFIG. 10 fit into their corresponding receptacles 112 in the other halfof the mold.

The mold half depicted in FIG. 11 has several pairs of mold cavities,each cavity being similar to the mold cavity depicted in FIG. 9. Themold cavities are of two types: first injection preform molding cavities114 and second injection preform coating cavities 120. The two types ofcavities are equal in number and are preferably arranged so that allcavities of one type are on the same side of the injection block 124 asbisected by the line between the alignment peg receptacles 112. Thisway, every preform molding cavity 114 is 180° away from a preformcoating cavity 120.

The mold half depicted in FIG. 10 has several mandrels 98, one for eachmold cavity (114 and 120). When the two halves which are FIGS. 10 and 11are put together, a mandrel 98 fits inside each cavity and serves as themold for the interior of the preform for the preform molding cavities114 and as a centering device for the uncoated preforms in preformcoating cavities 120. The mandrels 98 are mounted on a turntable 130which rotates 180° about its center so that a mandrel 98 originallyaligned with a preform molding cavity 114 will, after rotation, bealigned with a preform coating cavity 120, and vice-versa. As describedin greater detail below, this type of setup allows a preform to bemolded and then coated in a two-step process using the same piece ofequipment.

It should be noted that the drawings in FIGS. 10 and 11 are merelyillustrative. For instance, the drawings depict an apparatus havingthree molding cavities 114 and three coating cavities 120 (a 3/3 cavitymachine). However, the machines may have any number of cavities, as longas there are equal numbers of molding and coating cavities, for example12/12, 24/24, 48/48 and the like. The cavities may be arranged in anysuitable manner, as can be determined by one skilled in the art. Theseand other minor alterations are contemplated as part of this invention.

The two mold halves depicted in FIGS. 12 and 13 illustrate an embodimentof a mold of a 48/48 cavity machine as discussed for FIGS. 10 and 11.

Referring to FIG. 14 there is shown a perspective view of a mold of thetype for an overmolding (inject-over-inject) process in which themandrels 98 are partially located within the cavities 114 and 120. Thearrow shows the movement of the movable mold half 142, on which themandrels 98 lie, as the mold closes.

FIG. 15 shows a perspective view of a mold of the type used in anovermolding process, wherein the mandrels 98 are fully withdrawn fromthe cavities 114 and 120. The arrow indicates that the turntable 130rotates 180° to move the mandrels 98 from one cavity to the next. On thestationary half 144, the cooling for the preform molding cavity 114 isseparate from the cooling for the preform coating cavity 120. Both ofthese are separate from the cooling for the mandrels 98 in the movablehalf.

Referring to FIG. 16 there is shown a preferred three-layer preform 132.This embodiment of coated preform is preferably made by placing twocoating layers 134 and 136 on a preform 30 such as that shown in FIG. 1.

FIG. 17 schematically shows another preferred apparatus 150 which may beused in an overmolding process. A first and second injector 152, 154 aredisposed at the top of the machine 150 to provide a meltstream to firstand second mold cavities 156, 158. FIG. 18 shows a rotating table 160portion of the embodiment of FIG. 17. Four stations, labeled A throughD, each have a mandrel 98A-D formed thereon and are disposed on therotating table 160 roughly 90° in rotation apart. An actuator 162 suchas a hydraulic cylinder lifts the table 160 so that mandrels 98 from twostations are simultaneously inserted into the first and second moldcavities 156, 158. The mandrels 98 on the other stations remain clear ofany mold cavities. After the table 160 is lowered so that the mandrels98 are removed from the cavities, it then rotates 90°. Thus, the mandrel98 that was just removed from the first cavity 156 is placed in positionto be inserted into the second mold cavity 158 and the mandrel justremoved from the second cavity 158 is moved clear of the mold cavities.Each of the stations are cycled in turn through the first and secondmold cavities 156, 158 by a series of sequential 90° rotations. FIG. 19tracks the positions of the stations relative to each other during eachstep of a production cycle.

FIGS. 20 and 21 show another embodiment of an apparatus 170 of thepresent invention similar in many ways to that of FIGS. 17 and 18.However, in this embodiment, instead of the entire table 160 beinglifted by a hydraulic member, each station of the turntable 160 isindividually controlled by an actuator 172, and independently moved intoand out of engagement with a respective mold cavity. This arrangementallows for increased flexibility of the apparatus 170. For example, FIG.20 shows that a mandrel 98 may be held within the second cavity 158after a mandrel 98 in the first cavity 156 is removed therefrom. Thus,hold time between mold cavities can be independently optimized.

With next reference to FIGS. 22-23, a schematic view of anotherpreferred apparatus 250 which may be used to overmold multilayerpreforms is shown. In this embodiment, a rotating turntable 260 has astation (AA-DD) formed on each of four sides. Mold mandrels 98 or coresare disposed on each of the stations as in previous embodiments. Firstand second mold cavities 256, 258 are in communication withcorresponding first and second injection machines 252, 254 which supplymelt streams of PET and barrier material, respectively. The first moldcavity 256 is connected to the first injection machine 252 and remainsstationary; the second injection machine 254 is vertically orientedoverhead and also remains stationary. The turntable 260 is supported bya base member 264 which is horizontally movable upon ways 266 whichsupport the base member 264. The second mold cavity 258 is connected tothe turntable 260 by actuators 268 and also moves horizontally with theturntable 260. The actuators 268 pull the second mold cavity 258 intoengagement with a mandrel 98B disposed on the turntable 268 in order toclose the mold. After the second cavity 258 engages the correspondingmandrel, the turntable 260 next moves horizontally to engage a mandrelwith the first mold cavity 256. With both mold cavities engaged withmandrels, the mold is now completely closed, as shown in FIG. 23. Also,the second injection machine 254 is placed in communication with thesecond mold cavity 258 so that the second injection machine 254 canprovide a melt stream of barrier material thereto.

When injection is complete, the mold is opened. This is accomplished bythe turntable 260 first moving horizontally to disengage the mandrelfrom the first cavity 256, then raising the second mold out ofengagement with the turntable 260. The turntable 260 then rotates 90°and closure of the mold and injection of material is repeated. Injectedpreforms disposed on the mandrels 98 not engaged with mold cavities coolupon the associated mandrel during the rest of the cycle. The preformsare ejected before the associated mandrel is again brought intoengagement with the first mold cavity 256. FIG. 24 tracks the positionsof the stations relative to each other during each step of a productioncycle.

Referring to FIG. 25, there is shown a schematic of an apparatus whichmay be used to produce a meltstream comprised of numerous microlayers orlamellae in a lamellar injection molding (LIM) process as described infurther detail below.

With next reference to FIG. 26, a preferred embodiment of a mold mandrel298 and associated cavity 300 are shown. Cooling tubes 302 are formed ina spiral fashion just below the surface 304 of the mold cavity 300. Agate area 308 of the cavity 300 is defined near a gate 308 and an insert310 of a material with especially high heat transfer properties isdisposed in the cavity at the gate area 306. Thus, the injectedpreform's gate area/base end 314 is cooled especially quickly.

The mandrel 298 is hollow and has a wall 320 of generally uniformthickness. A bubbler cooling arrangement 330 is disposed within thehollow mandrel 298 and comprises a core tube 332 located centrallywithin the mandrel 298 which delivers chilled coolant C directly to abase end 322 of the mandrel 298. Coolant C works its way up the mandrelfrom the base end 322 and exits through an output line 334. The coretube is held in place by ribs 336 extending between the tube and themandrel wall 320.

Referring also to FIGS. 27 and 28, an air insertion system 340 is shownformed at a joint 342 between members of the mold cavity 300. A notch344 is formed circumferentially around the cavity 300. The notch 344 issufficiently small that substantially no molten plastic will enterduring melt injection. An air line 350 connects the notch 344 to asource of air pressure and a valve regulates the supply of air to thenotch 344. During melt injection, the valve is closed. When injection iscomplete, the valve is opened and pressurized air A is supplied to thenotch 344 in order to defeat a vacuum that may form between an injectedpreform and the cavity wall 304.

The preferred method and apparatus for making barrier coated preforms isdiscussed in more detail below. Because the methods and apparatus areespecially preferred for use in forming barrier coated bottlescomprising certain preferred materials, the physical characteristics,identification, preparation and enhancement of the preferred materialsis discussed prior to the preferred methods and apparatus for workingwith the materials.

C. Physical Characteristics of Preferred Barrier Materials

Preferred barrier materials in accordance with the present inventionpreferably exhibit several physical characteristics which allow for thebarrier coated bottles and articles of the present invention to be ableto withstand processing and physical stresses in a manner similar orsuperior to that of uncoated PET articles, in addition to producingarticles which are cosmetically appealing and have excellent barrierproperties.

Adhesion is the union or sticking together of two surfaces. The actualinterfacial adhesion is a phenomenon which occurs at the microscopiclevel. It is based upon molecular interactions and depends upon chemicalbonding, van der Waals forces and other intermolecular attractive forcesat the molecular level.

Good adhesion between the barrier layer and the PET layer is especiallyimportant when the article is a barrier bottle made by blow-molding apreform. If the materials adhere well, then they will act as one unitwhen they are subjected to a blow molding process and as they aresubjected to stresses when existing in the form of a container. Wherethe adhesion is poor, delamination results either over time or underphysical stress such as squeezing the container or the containerjostling during shipment. Delamination is not only unattractive from acommercial standpoint, it may be evidence of a lack of structuralintegrity of the container. Furthermore, good adhesion means that thelayers will stay in close contact when the container is expanded duringthe molding process and will move as one unit. When the two materialsact in such a manner, it is less likely that there will be voids in thecoating, thus allowing a thinner coating to be applied. The barriermaterials preferably adhere sufficiently to PET such that the barrierlayer cannot be easily pulled apart from the PET layer at 22° C.

Thus, due in part to the direct adhesion of the barrier layer to thePET, the present invention differs from that disclosed by Farha in U.S.Pat. No. 5,472,753. In Farha, there is not disclosed, nor is thesuggestion made, that the phenoxy-type thermoplastic can or should bebound directly to the PET without being blended with the copolyester orusing the copolyester as a tie layer or that a copolyester itself couldbe used as a barrier material.

The glass transition temperature (Tg) is defined as the temperature atwhich a non-crystallizable polymer undergoes the transformation from asoft rubber state to a hard elastic polymer glass. In a range oftemperatures above its Tg, a material will become soft enough to allowit to flow readily when subjected to an external force or pressure, yetnot so soft that its viscosity is so low that it acts more like a liquidthan a pliable solid. The temperature range above Tg is the preferredtemperature range for performing a blow-molding process, as the materialis soft enough to flow under the force of the air blown into the preformto fit the mold but not so soft that it breaks up or becomes uneven intexture. Thus, when materials have similar glass transitiontemperatures, they will have similar preferred blowing temperatureranges, allowing the materials to be processed together withoutcompromising the performance of either material.

In the blow-molding process to produce bottle from a preform, as isknown in the art, the preform is heated to a temperature slightly abovethe Tg of the preform material so that when air is forced into thepreform's interior, it will be able to flow to fill the mold in which itis placed. If one does not sufficiently heat the preform and uses atemperature below the Tg, the preform material will be too hard to flowproperly, and would likely crack, craze, or not expand to fill the mold.Conversely, if one heats the preform to a temperature well above the Tg,the material would likely become so soft that it would not be able tohold its shape and would process improperly.

If a barrier coating material has a Tg similar to that of PET, it willhave a blowing temperature range similar to PET. Thus, if a PET preformis coated with such a barrier material, a blowing temperature can bechosen that allows both materials to be processed within their preferredblowing temperature ranges. If the barrier coating were to have a Tgdissimilar to that of PET, it would be difficult, if not impossible, tochoose a blowing temperature suitable for both materials. When thebarrier coating materials have a Tg similar to PET, the coated preformbehaves during blow molding as if it were made of one material,expanding smoothly and creating a cosmetically appealing container withan even thickness and uniform coating of the barrier material where itis applied.

The glass transition temperature of PET occurs in a window of about75-85° C., depending upon how the PET has been processed previously. TheTg for preferred barrier materials of embodiments of the presentinvention is preferably 55 to 140° C., more preferably 90 to 110° C.

Another factor which has an impact on the performance of barrierpreforms during blow molding is the state of the material. The preferredbarrier materials of preferred embodiments of the present invention areamorphous rather than crystalline. This is because materials in anamorphous state are easier to form into bottles and containers by use ofa blow molding process than materials in a crystalline state. PET canexist in both crystalline and amorphous forms. However, in embodimentsof the present invention it is highly preferred that the crystallinityof the PET be minimized and the amorphous state maximized in order tocreate a semi-crystalline state which, among other things, aidsinterlayer adhesion and in the blow molding process. A PET articleformed from a melt of PET, as in injection molding, can be guided into asemi-crystalline form by cooling the melt at a high rate, fast enough toquench the crystallization process, freezing the PET in a mostlyamorphous state. Additionally, use of “high IPA PET” as describedearlier herein will allow easier quenching of the crystallizationprocess because it crystallizes at a lower rate than homopolymer PET.

Intrinsic viscosity and melt index are two properties which are relatedto a polymer's molecular weight. These properties give an indication asto how materials will act under various processing conditions, such asinjection molding and blow molding processes.

Barrier materials for use in the articles and methods of the presentinvention have an intrinsic viscosity of preferably 0.70-0.90 dl/g, morepreferably 0.74-0.87 dl/g, most preferably 0.84-0.85 dl/g and a meltindex of preferably 5-30, more preferably 7-12, most preferably 10.

Barrier materials of embodiments of the present invention preferablyhave tensile strength and creep resistance similar to PET. Similarity inthese physical properties allows the barrier coating to act as more thansimply a gas barrier. A barrier coating having physical propertiessimilar to PET acts as a structural component of the container, allowingthe barrier material to displace some of the polyethylene terephthalatein the container without sacrificing container performance. Displacementof PET allows for the resulting barrier-coated containers to havephysical performance and characteristics similar to their uncoatedcounterparts without a substantial change in weight or size. It alsoallows for any additional cost from adding the barrier material to bedefrayed by a reduction in the cost per container attributed to PET.

Similarity in tensile strength between PET and the barrier coatingmaterials helps the container to have structural integrity. This isespecially important if some PET is displaced by barrier material.Barrier-coated bottles and containers having features in accordance withthe present invention are able to withstand the same physical forces asan uncoated container, allowing, for example, barrier-coated containersto be shipped and handled in the customary manner of handling uncoatedPET containers. If the barrier-coating material were to have a tensilestrength substantially lower than that of PET, a container having somePET displaced by barrier material would likely not be able to withstandthe same forces as an uncoated container.

Similarity in creep resistance between PET and the barrier coatingmaterials helps the container to retain its shape. Creep resistancerelates to the ability of a material to resist changing its shape inresponse to an applied force. For example, a bottle which holds acarbonated liquid needs to be able to resist the pressure of dissolvedgas pushing outward and retain its original shape. If the barriercoating material were to have a substantially lower resistance to creepthan PET in a container, the resulting container would be more likely todeform over time, reducing the shelf-life of the product.

For applications where optical clarity is of importance, preferredbarrier materials have an index of refraction similar to that of PET.When the refractive index of the PET and the barrier coating materialare similar, the preforms and, perhaps more importantly, the containersblown therefrom are optically clear and, thus, cosmetically appealingfor use as a beverage container where clarity of the bottle isfrequently desired. If, however, the two materials have substantiallydissimilar refractive indices when they are placed in contact with eachother, the resulting combination will have visual distortions and may becloudy or opaque, depending upon the degree of difference in therefractive indices of the materials.

Polyethylene terephthalate has an index of refraction for visible lightwithin the range of about 1.40 to 1.75, depending upon its physicalconfiguration. When made into preforms, the refractive index ispreferably within the range of about 1.55 to 1.75, and more preferablyin the range of 1.55-1.65. After the preform is made into a bottle, thewall of the final product, may be characterized as a biaxially-orientedfilm since it is subject to both hoop and axial stresses in the blowmolding operation. Blow molded PET generally exhibits a refractive indexwithin the range of about 1.40 to 1.75, usually about 1.55 to 1.75,depending upon the stretch ratio involved in the blow molding operation.For relatively low stretch ratios of about 6:1, the refractive indexwill be near the lower end, whereas for high stretch ratios, about 10:1,the refractive index will be near the upper end of the aforementionedrange. It will be recognized that the stretch ratios referred to hereinare biaxial stretch ratios resulting from and include the product of thehoop stretch ratio and the axial stretch ratio. For example, in a blowmolding operation in which the final preform is enlarged by a factor of2.5 in the axial direction and a factor of 3.5 diametrically, thestretch ratio will be about 8.75 (2.5.times.3.5).

Using the designation n_(i) to indicate the refractive index for PET andn_(o) to indicate the refractive index for the barrier material, theratio between the values n_(i) and n_(o) is preferably 0.8-1.3, morepreferably 1.0-1.2, most preferably 1.0-1.1. As will be recognized bythose skilled in the art, for the ratio n_(i)/n_(o)=1 the distortion dueto refractive index will be at a minimum, because the two indices areidentical. As the ratio progressively varies from one, however, thedistortion increases progressively.

D. Preferred Barrier Coating Materials and their Preparation

The preferred barrier coating materials for use in the articles andmethods of the present invention include Phenoxy-type Thermoplasticmaterials, copolyesters of terephthalic acid, isophthalic acid, and atleast one diol having good barrier properties as compared to PET(Copolyester Barrier Materials), Polyamides, PEN, PEN copolymers,PEN/PET blends, and combinations thereof. Preferably, the Phenoxy-typeThermoplastics used as barrier materials in the present invention areone of the following types:

(1) hydroxy-functional poly(amide ethers) having repeating unitsrepresented by any one of the Formulae Ia, Ib or Ic:

(2) poly(hydroxy amide ethers) having repeating units representedindependently by any one of the Formulae IIa, IIb or IIc:

(3) amide- and hydroxymethyl-functionalized polyethers having repeatingunits represented by Formula III:

(4) hydroxy-functional polyethers having repeating units represented byFormula IV:

(5) hydroxy-functional poly(ether sulfonamides) having repeating unitsrepresented by Formulae Va or Vb:

(6) poly(hydroxy ester ethers) having repeating units represented byFormula VI:

(7) hydroxy-phenoxyether polymers having repeating units represented byFormula VII:

and

(8) poly(hydroxyamino ethers) having repeating units represented byFormula VIII:

wherein each Ar individually represents a divalent aromatic moiety,substituted divalent aromatic moiety or heteroaromatic moiety, or acombination of different divalent aromatic moieties, substitutedaromatic moieties or heteroaromatic moieties; R is individually hydrogenor a monovalent hydrocarbyl moiety; each Ar₁ is a divalent aromaticmoiety or combination of divalent aromatic moieties bearing amide orhydroxymethyl groups; each Ar₂ is the same or different than Ar and isindividually a divalent aromatic moiety, substituted aromatic moiety orheteroaromatic moiety or a combination of different divalent aromaticmoieties, substituted aromatic moieties or heteroaromatic moieties; R₁is individually a predominantly hydrocarbylene moiety, such as adivalent aromatic moiety, substituted divalent aromatic moiety, divalentheteroaromatic moiety, divalent alkylene moiety, divalent substitutedalkylene moiety or divalent heteroalkylene moiety or a combination ofsuch moieties; R₂ is individually a monovalent hydrocarbyl moiety; A isan amine moiety or a combination of different amine moieties; X is anamine, an arylenedioxy, an arylenedisulfonamido or an arylenedicarboxymoiety or combination of such moieties; and Ar₃ is a “cardo” moietyrepresented by any one of the Formulae:

wherein Y is nil, a covalent bond, or a linking group, wherein suitablelinking groups include, for example, an oxygen atom, a sulfur atom, acarbonyl atom, a sulfonyl group, or a methylene group or similarlinkage; n is an integer from about 10 to about 1000; x is 0.01 to 1.0;and y is 0 to 0.5.

The term “predominantly hydrocarbylene” means a divalent radical that ispredominantly hydrocarbon, but which optionally contains a smallquantity of a heteroatomic moiety such as oxygen, sulfur, imino,sulfonyl, sulfoxyl, and the like.

The hydroxy-functional poly(amide ethers) represented by Formula I arepreferably prepared by contacting an N,N′-bis(hydroxyphenylamido)alkaneor arene with a diglycidyl ether as described in U.S. Pat. Nos.5,089,588 and 5,143,998.

The poly(hydroxy amide ethers) represented by Formula II are prepared bycontacting a bis(hydroxyphenylamido)alkane or arene, or a combination of2 or more of these compounds, such as N,N′-bis(3-hydroxyphenyl)adipamide or N,N′-bis(3-hydroxyphenyl)glutaramide, with an epihalohydrinas described in U.S. Pat. No. 5,134,218.

The amide- and hydroxymethyl-functionalized polyethers represented byFormula III can be prepared, for example, by reacting the diglycidylethers, such as the diglycidyl ether of bisphenol A, with a dihydricphenol having pendant amido, N-substituted amido and/or hydroxyalkylmoieties, such as 2,2-bis(4-hydroxyphenyl)acetamide and3,5-dihydroxybenzamide. These polyethers and their preparation aredescribed in U.S. Pat. Nos. 5,115,075 and 5,218,075.

The hydroxy-functional polyethers represented by Formula IV can beprepared, for example, by allowing a diglycidyl ether or combination ofdiglycidyl ethers to react with a dihydric phenol or a combination ofdihydric phenols using the process described in U.S. Pat. No. 5,164,472.Alternatively, the hydroxy-functional polyethers are obtained byallowing a dihydric phenol or combination of dihydric phenols to reactwith an epihalohydrin by the process described by Reinking, Barnabeo andHale in the Journal of Applied Polymer Science, Vol. 7, p. 2135 (1963).

The hydroxy-functional poly(ether sulfonamides) represented by Formula Vare prepared, for example, by polymerizing an N,N′-dialkyl orN,N′-diaryldisulfonamide with a diglycidyl ether as described in U.S.Pat. No. 5,149,768.

The poly(hydroxy ester ethers) represented by Formula VI are prepared byreacting diglycidyl ethers of aliphatic or aromatic diacids, such asdiglycidyl terephthalate, or diglycidyl ethers of dihydric phenols with,aliphatic or aromatic diacids such as adipic acid or isophthalic acid.These polyesters are described in U.S. Pat. No. 5,171,820.

The hydroxy-phenoxyether polymers represented by Formula VII areprepared, for example, by contacting at least one dinucleophilic monomerwith at least one diglycidyl ether of a cardo bisphenol, such as9,9-bis(4-hydroxyphenyl)fluorene, phenolphthalein, orphenolphthalimidine or a substituted cardo bisphenol, such as asubstituted bis(hydroxyphenyl)fluorene, a substituted phenolphthalein ora substituted phenolphthalimidine under conditions sufficient to causethe nucleophilic moieties of the dinucleophilic monomer to react withepoxy moieties to form a polymer backbone containing pendant hydroxymoieties and ether, imino, amino, sulfonamido or ester linkages. Thesehydroxy-phenoxyether polymers are described in U.S. Pat. No. 5,184,373.

The poly(hydroxyamino ethers) (“PHAE” or polyetheramines) represented byFormula VIII are prepared by contacting one or more of the diglycidylethers of a dihydric phenol with an amine having two amine hydrogensunder conditions sufficient to cause the amine moieties to react withepoxy moieties to form a polymer backbone having amine linkages, etherlinkages and pendant hydroxyl moieties. These compounds are described inU.S. Pat. No. 5,275,853.

Phenoxy-type Thermoplastics of Formulae I-VIII may be acquired from DowChemical Company (Midland, Mich. U.S.A.).

The Phenoxy-type Thermoplastics commercially available from PhenoxyAssociates, Inc. are suitable for use in the present invention. Thesehydroxy-phenoxyether polymers are the condensation reaction products ofa dihydric polynuclear phenol, such as bisphenol A, and an epihalohydrinand have the repeating units represented by Formula IV wherein Ar is anisopropylidene diphenylene moiety. The process for preparing these isdescribed in U.S. Pat. No. 3,305,528, incorporated herein by referencein its entirety.

The most preferred Phenoxy-type Thermoplastics are the poly(hydroxyaminoethers) (“PHAE”) represented by Formula VIII. An example is that sold asXU19040.00L by Dow Chemical Company.

Examples of preferred Copolyester Barrier Materials and a process fortheir preparation is described in U.S. Pat. No. 4,578,295 to Jabarin.They are generally prepared by heating a mixture of at least onereactant selected from isophthalic acid, terephthalic acid and their C₁to C₄ alkyl esters with 1,3 bis(2-hydroxyethoxy)benzene and ethyleneglycol. Optionally, the mixture may further comprise one or moreester-forming dihydroxy hydrocarbon and/orbis(4-β-hydroxyethoxyphenyl)sulfone. Especially preferred CopolyesterBarrier Materials are available from Mitsui Petrochemical Ind. Ltd.(Japan) as B-010, B-030 and others of this family.

Examples of preferred Polyamide barrier materials include MXD-6 fromMitsubishi Gas Chemical (Japan). Other preferred Polyamide barriermaterials are polyamides containing preferably 1-10% polyester, morepreferably 1-2% polyester by weight, where the polyester is preferablyPET, more preferably high IPA PET. These materials are made by addingthe polyester to the polyamide polycondensation mixture. “Polyamide” asused herein shall include those polyamides containing PET or otherpolyesters.

Other preferred barrier materials include polyethylene naphthalate(PEN), PEN copolyester, and PET/PEN blends. PEN materials can bepurchased from Shell Chemical Company.

E. Preparation of Polyesters

Polyesters and methods for their preparation (including the specificmonomers employed in their formation, their proportions, polymerizationtemperatures, catalysts and other conditions) are well-known in the artand reference is made thereto for the purposes of this invention. Forpurposes of illustration and not limitation, reference is particularlymade to pages 1-62 of Volume 12 of the Encyclopedia of Polymer Scienceand Engineering, 1988 revision, John Wiley & Sons.

Typically, polyesters are derived from the reaction of a di- orpolycarboxylic acid with a di- or polyhydric alcohol. Suitable di- orpolycarboxylic acids include polycarboxylic acids and the esters andanthydrides of such acids, and mixture thereof. Representativecarboxylic acids include phthalic, isophthalic, adipic azelaic,terephthalic, oxalic, malonic, succinic, glutaric, sebacic, and thelike. Dicarboxylic components are preferred. Terephthalic acid is mostcommonly employed and preferred in the preparation of polyester films.α,β-Unsaturated di- and polycarboxylic acids (including esters oranthydrides of such acids and mixtures thereof) can be used as partialreplacement for the saturated carboxylic components. Representativeα,β-unsaturated di- and polycarboxylic acids include maleic, fumaric,aconitic, itaconic, mesaconic, citraconic, monochloromaleic and thelike.

Typical di- and polyhydric alcohols used to prepare the polyester arethose alcohols having at least two hydroxy groups, although minoramounts of alcohol having more or less hydroxy groups may be used.Dihydroxy alcohols are preferred. Dihydroxy alcohols conventionallyemployed in the preparation of polyesters include diethylene glycol;dipropylene glycol; ethylene glycol; 1,2-propylene glycol;1,4-butanediol; 1,4-pentanediol; 1,5-hexanediol,1,4-cyclohexanedimethano-1 and the like with 1,2-propylene glycol beingpreferred. Mixtures of the alcohols can also be employed. The di- orpolyhydric alcohol component of the polyester is usually stoichiometricor in slight excess with respect to the acid. The excess of the di- orpolyhydric alcohol will seldom exceed about 20 to 25 mole percent andusually is between about 2 and about 10 mole percent.

The polyester is generally prepared by heating a mixture of the di- orpolyhydric alcohol and the di- or polycarboxylic component in theirproper molar ratios at elevated temperatures, usually between about 100°C. and 250° C. for extended periods of time, generally ranging from 5 to15 hours. Polymerization inhibitors such as t-butylcatechol mayadvantageously be used.

PET, the preferred polyester, which is commonly made by condensation ofterephthalic acid and ethylene glycol, may be purchased from DowChemical Company (Midland, Mich.), and Allied Signal Inc. (Baton Rouge,La.), among many others.

Preferably, the PET used is that in which isophthalic acid (IPA) isadded during the manufacture of the PET to form a copolymer. The amountof IPA added is preferably 2-10% by weight, more preferably 3-8% byweight, most preferably 4-5% by weight. The most preferred range isbased upon current FDA regulations which currently do not allow for PETmaterials having an IPA content of more than 5% to be in contact withfood or drink. High-IPA PET (PET having more than about 2% IPA byweight) can be made as discussed above, or purchased from a number ofdifferent manufacturers, for instance PET with 4.8% IPA may be purchasedfrom SKF (Italy) and 10% IPA PET may be purchased from INCA (DowEurope).

Additionally, if a Polyamide is chosen as the barrier material, it ispreferred to use a polyamide-containing polyester. Suchpolyamide-containing polyesters are formed by adding polyamide to thepolyester polycondensation mixture. The amount of polyamide in thepolyester is preferably 1-10% by weight, more preferably 1-2% by weight.The polyester used is preferably PET, more preferably high IPA PET.

F. Materials to Enhance Barrier Properties of Barrier Resins

The barrier materials disclosed above may be used in combination withother materials which enhance the barrier properties. Generallyspeaking, one cause for the diffusion of gases through a material is theexistence of gaps or holes in the material at the molecular levelthrough which the gas molecules can pass. The presence of intermolecularforces in a material, such as hydrogen bonding, allows for interchaincohesion in the matrix which closes these gaps and discourages diffusionof gases. One may also increase the gas-barrier ability of good barriermaterials by adding an additional molecule or substance which takesadvantage of such intermolecular forces and acts as a bridge betweenpolymer chains in the matrix, thus helping to close the holes in thematrix and reduce gas diffusion.

Derivatives of the diol resorcinol (m-dihydroxybenzene), when reactedwith other monomers in the manufacture of PHAE, PET, Copolyester BarrierMaterials, and other barrier materials, will generally result in amaterial which has better barrier properties than the same material ifit does not contain the resorcinol derivative. For example, resorcinoldiglycidyl ether can be used in PHAE and hydroxyethyl ether resorcinolcan be used in PET and other polyesters and Copolyester BarrierMaterials.

One measure of the efficacy of a barrier is the effect that it has uponthe shelf life of the material. The shelf life of a carbonated softdrink in a 32 oz PET non-barrier bottle is approximately 12-16 weeks.Shelf life is determined as the time at which less than 85% of theoriginal amount of carbon dioxide is remaining in the bottle. Bottlescoated with PHAE using the inject-over-inject method described belowhave been found to have a shelf life 2 to 3 times greater than that ofPET alone. If, however, PHAE with resorcinol diglycidyl ether is used,the shelf life can be increased to 4 to 5 times that of PET alone.

Another way of enhancing the barrier properties of a material is to adda substance which “plugs” the holes in the polymer matrix and thusdiscourages gases from passing through the matrix. Alternatively, asubstance may aid in creating a more tortuous path for gas molecules totake as they permeate a material. One such substance, referred to hereinby the term “Nanoparticles” or “nanoparticular material” are tinyparticles of materials which enhance the barrier properties of amaterial by creating a more tortuous path for migrating oxygen or carbondioxide. One preferred type of nanoparticular material is amicroparticular clay-based product available from Southern ClayProducts.

G. Preparing Barrier-Coated Articles

Once a suitable barrier coating material is chosen, the coated preformmust be made in a manner that promotes adhesion between the twomaterials. Generally, adherence between the barrier coating materialsand PET increases as the surface temperature of the PET increases.Therefore, it is preferable to perform coating on heated preforms,although the preferred barrier materials will adhere to PET at roomtemperature.

There are a number of methods of producing a coated PET preform inaccordance with the present invention. Preferred methods include dipcoating, spray coating, flame spraying fluidized bed dipping, andelectrostatic powder spraying. Another preferred method, lamellarinjection molding, is discussed in more detail below. Each of the abovemethods is introduced and described in my copending U.S. applicationSer. No. 09/147,971, which was filed on Oct. 19, 1998, entitledBARRIER-COATED POLYESTER, which is hereby incorporated by reference inits entirety.

An especially preferred method of producing a coated PET preform isreferred to herein generally as overmolding, and sometimes asinject-over-inject (“IOI”). The name refers to a procedure which usesinjection molding to inject one or more layers of barrier material overan existing preform, which preferably was itself made by injectionmolding. The terms “overinjecting” and “overmolding” are used herein todescribe the coating process whereby a layer of material, preferablycomprising barrier material, is injected over an existing preform. In anespecially preferred embodiment, the overinjecting process is performedwhile the underlying preform has not yet fully cooled. Overinjecting maybe used to place one or more additional layers of materials such asthose comprising barrier material, recycled PET, or other materials overa coated or uncoated preform.

The overmolding is carried out by using an injection molding processusing equipment similar to that used to form the uncoated preformitself. A preferred mold for overmolding, with an uncoated preform inplace is shown in FIG. 9. The mold comprises two halves, a cavity half92 and a mandrel half 94, and is shown in FIG. 9 in the closed positionprior to overinjecting. The cavity half 92 comprises a cavity in whichthe uncoated preform is placed. The support ring 38 of the preform restson a ledge 96 and is held in place by the mandrel half 94, which exertspressure on the support ring 38, thus sealing the neck portion off fromthe body portion of the preform. The cavity half 92 has a plurality oftubes or channels 104 therein which carry a fluid. Preferably the fluidin the channels circulates in a path in which the fluid passes into aninput in the cavity half 92, through the channels 104, out of the cavityhalf 92 through an output, through a chiller or other cooling device,and then back into the input. The circulating fluid serves to cool themold, which in turn cools the plastic melt which is injected into themold to form the coated preform.

The mandrel half 94 of the mold comprises a mandrel 98. The mandrel 98,sometimes called a core, protrudes from the mandrel half 94 of the moldand occupies the central cavity of the preform. In addition to helpingto center the preform in the mold, the mandrel 98 cools the interior ofthe preform. The cooling is done by fluid circulating through channels106 in the mandrel half 94 of the mold, most importantly through thelength of the mandrel 98 itself. The channels 106 of the mandrel half 94work in a manner similar to the channels 104 in the cavity half 92, inthat they create the portion of the path through which the cooling fluidtravels which lies in the interior of the mold half.

As the preform sits in the mold cavity, the body portion of the preformis centered within the cavity and is completely surrounded by a voidspace 100. The preform, thus positioned, acts as an interior die mandrelin the subsequent injection procedure. The melt of the overmoldingmaterial, preferably comprising a barrier material, is then introducedinto the mold cavity from the injector via gate 102 and flows around thepreform, preferably surrounding at least the body portion 34 of thepreform. Following overinjection, the overmolded layer will take theapproximate size and shape of the void space 100.

To carry out the overmolding procedure, one preferably heats the initialpreform which is to be coated preferably to a temperature above its Tg.In the case of PET, that temperature is preferably 100 to 200° C., morepreferably 180-225° C. If a temperature at or above the temperature ofcrystallization for PET is used, which is about 120° C., care should betaken when cooling the PET in the preform. The cooling should besufficient to minimize crystallization of the PET in the preform so thatthe PET is in the preferred semi-crystalline state. Alternatively, theinitial preform used may be one which has been very recently injectionmolded and not fully cooled, as to be at an elevated temperature as ispreferred for the overmolding process.

The coating material is heated to form a melt of a viscosity compatiblewith use in an injection molding apparatus. The temperature for this,the inject temperature, will differ among materials, as melting rangesin polymers and viscosities of melts may vary due to the history,chemical character, molecular weight, degree of branching and othercharacteristics of a material. For the preferred barrier materialsdisclosed above, the inject temperature is preferably in the range ofabout 160-325° C., more preferably 200 to 275° C. For example, for theCopolyester Barrier Material B-010, the preferred temperature is around210° C., whereas for the PHAE XU-19040.00L the preferred temperature isin the range of 160-260° C., and is more preferably about 200-280° C.Most preferably, the PHAE inject temperature is about 190-230° C. Ifrecycled PET is used, the inject temperature is preferably 250-300° C.The coating material is then injected into the mold in a volumesufficient to fill the void space 100. If the coating material comprisesbarrier material, the coating layer is a barrier layer.

The coated preform is preferably cooled at least to the point where itcan be displaced from the mold or handled without being damaged, andremoved from the mold where further cooling may take place. If PET isused, and the preform has been heated to a temperature near or above thetemperature of crystallization for PET, the cooling should be fairlyrapid and sufficient to ensure that the PET is primarily in thesemi-crystalline state when the preform is fully cooled. As a result ofthis process, a strong and effective bonding takes place between theinitial preform and the subsequently applied coating material.

Overmolding can be also used to create coated preforms with three ormore layers. In FIG. 16, there is shown a three-layer embodiment of apreform 132 in accordance with the present invention. The preform showntherein has two coating layers, a middle layer 134 and an outer layer134. The relative thickness of the layers shown in FIG. 16 may be variedto suit a particular combination of layer materials or to allow for themaking of different sized bottles. As will be understood by one skilledin the art, a procedure analogous to that disclosed above would befollowed, except that the initial preform would be one which had alreadybeen coated, as by one of the methods for making coated preformsdescribed herein, including overmolding.

1. First Preferred Method and Apparatus for Overmolding

A first preferred apparatus for performing the overmolding process isbased upon the use of a 330-330-200 machine by Engel (Austria). Thepreferred mold portion the machine is shown schematically in FIGS. 10-15and comprises a movable half 142 and a stationary half 144. Both halvesare preferably made from hard metal. The stationary half 144 comprisesat least two mold sections 146, 148, wherein each mold section comprisesN (N>0) identical mold cavities 114, 120, an input and output forcooling fluid, channels allowing for circulation of cooling fluid withinthe mold section, injection apparatus, and hot runners channeling themolten material from the injection apparatus to the gate of each moldcavity. Because each mold section forms a distinct preform layer, andeach preform layer is preferably made of a different material, each moldsection is separately controlled to accommodate the potentiallydifferent conditions required for each material and layer. The injectorassociated with a particular mold section injects a molten material, ata temperature suitable for that particular material, through that moldsection's hot runners and gates and into the mold cavities. The moldsection's own input and output for cooling fluid allow for changing thetemperature of the mold section to accommodate the characteristics ofthe particular material injected into a mold section. Consequently, eachmold section may have a different injection temperature, moldtemperature, pressure, injection volume, cooling fluid temperature, etc.to accommodate the material and operational requirements of a particularpreform layer.

The movable half 142 of the mold comprises a turntable 130 and aplurality of cores or mandrels 98. The alignment pins guide the movablehalf 142 to slidably move in a preferably horizontal direction towardsor away from the stationary half 144. The turntable 130 may rotate ineither a clockwise or counterclockwise direction, and is mounted ontothe movable half 142. The plurality of mandrels 98 are affixed onto theturntable 130. These mandrels 98 serve as the mold form for the interiorof the preform, as well as serving as a carrier and cooling device forthe preform during the molding operation. The cooling system in themandrels is separate from the cooling system in the mold sections.

The mold temperature or cooling for the mold is controlled bycirculating fluid. There is separate cooling fluid circulation for themovable half 142 and for each of the mold sections 146, 148 of thestationary half 144. Therefore, in a mold having two mold sections inthe stationary half 144, there is separate cooling for each of the twomold sections plus separate cooling for the movable half 142 of themold. Analogously, in a mold having three mold sections in thestationary half, there are four separate cooling fluid circulation setups: one for each mold section, for a total of three, plus one for themovable half 142. Each cooling fluid circulation set up works in asimilar manner. The fluid enters the mold, flows through a network ofchannels or tubes inside as discussed above for FIG. 9, and then exitsthrough an output. From the output, the fluid travels through a pump,which keeps the fluid flowing, and a chilling system to keep the fluidwithin the desired temperature range, before going back into the mold.

In a preferred embodiment, the mandrels and cavities are constructed ofa high heat transfer material, such a beryllium, which is coated with ahard metal, such as tin or chrome. The hard coating keeps the berylliumfrom direct contact with the preform, as well as acting as a release forejection and providing a hard surface for long life. The high heattransfer material allows for more efficient cooling, and thus assists inachieving lower cycle times. The high heat transfer material may bedisposed over the entire area of each mandrel and/or cavity, or it maybe only on portions thereof. Preferably at least the tips of themandrels comprise high heat transfer material. Another, even morepreferred high heat transfer material is Ampcoloy, which is commerciallyavailable from Uudenholm, Inc.

The number of mandrels is equal to the total number of cavities, and thearrangement of the mandrels 98 on the movable half 142 mirrors thearrangement of the cavities 114, 120 on the stationary half 144. Toclose the mold, the movable half 142 moves towards the stationary half144, mating the mandrels 98 with the cavities 114, 120. To open themold, the movable half 142 moves away from the stationary half 144 suchthat the mandrels 98 are well clear of the block on the stationary half144. After the mandrels are fully withdrawn 98 from the mold sections146, 148, the turntable 130 of the movable half 142 rotates the mandrels98 into alignment with a different mold section. Thus, the movable halfrotates 360°/(number of mold sections in the stationary half) degreesafter each withdrawal of the mandrels from the stationary half. When themachine is in operation, during the withdrawal and rotation steps, therewill be preforms present on some or all of the mandrels.

The size of the cavities in a given mold section 146, 148 will beidentical; however the size of the cavities will differ among the moldsections. The cavities in which the uncoated preforms are first molded,the preform molding cavities 114, are smallest in size. The size of thecavities 120 in the mold section 148 in which the first coating step isperformed are larger than the preform molding cavities 114, in order toaccommodate the uncoated preform and still provide space for the coatingmaterial to be injected to form the overmolded coating. The cavities ineach subsequent mold section wherein additional overmolding steps areperformed will be increasingly larger in size to accommodate the preformas it gets larger with each coating step.

After a set of preforms has been molded and overmolded to completion, aseries of ejectors eject the finished preforms off of the mandrels 98.The ejectors for the mandrels operate independently, or at least thereis a single ejector for a set of mandrels equal in number andconfiguration to a single mold section, so that only the completedpreforms are ejected. Uncoated or incompletely-coated preforms remain onthe mandrels so that they may continue in the cycle to the next moldsection. The ejection may cause the preforms to completely separate fromthe mandrels and fall into a bin or onto a conveyor. Alternatively, thepreforms may remain on the mandrels after ejection, after which arobotic arm or other such apparatus grasps a preform or group ofpreforms for removal to a bin, conveyor, or other desired location.

FIGS. 10 and 11 illustrate a schematic for an embodiment of theapparatus described above. FIG. 11 is the stationary half 144 of themold. In this embodiment, the block 124 has two mold sections, onesection 146 comprising a set of three preform molding cavities 114 andthe other section 148 comprising a set of three preform coating cavities120. Each of the preform coating cavities 120 is preferably like thatshown in FIG. 9, discussed above. Each of the preform molding cavities114 is preferably similar to that shown in FIG. 9, in that the materialis injected into a space defined by the mandrel 98 (albeit without apreform already thereon) and the wall of the mold which is cooled byfluid circulating through channels inside the mold block. Consequently,one full production cycle of this apparatus will yield three two-layerpreforms. If more than three preforms per cycle is desired, thestationary half can be reconfigured to accommodate more cavities in eachof the mold sections. An example of this is seen in FIG. 13, whereinthere is shown a stationary half of a mold comprising two mold sections,one 146 comprising forty-eight preform molding cavities 114 and theother 148 comprising forty-eight preform coating cavities 120. If athree or more layer preform is desired, the stationary half 144 can bereconfigured to accommodate additional mold sections, one for eachpreform layer

FIG. 10 illustrates the movable half 142 of the mold. The movable halfcomprises six identical mandrels 98 mounted on the turntable 130. Eachmandrel 98 corresponds to a cavity on the stationary half 144 of themold. The movable half also comprises alignment pegs 110, whichcorrespond to the receptacles 112 on the stationary half 144. When themovable half 142 of the mold moves to close the mold, the alignment pegs110 are mated with their corresponding receptacles 112 such that themolding cavities 114 and the coating cavities 120 align with themandrels 98. After alignment and closure, half of the mandrels 98 arecentered within preform molding cavities 114 and the other half of themandrels 98 are centered within preform coating cavities 120.

The configuration of the cavities, mandrels, and alignment pegs andreceptacles must all have sufficient symmetry such that after the moldis separated and rotated the proper number of degrees, all of themandrels line up with cavities and all alignment pegs line up withreceptacles. Moreover, each mandrel must be in a cavity in a differentmold section than it was in prior to rotation in order to achieve theorderly process of molding and overmolding in an identical fashion foreach preform made in the machine.

Two views of the two mold halves together are shown in FIGS. 14 and 15.In FIG. 14, the movable half 142 is moving towards the stationary half144, as indicated by the arrow. Two mandrels 98, mounted on theturntable 130, are beginning to enter cavities, one enters a moldingcavity 114 and the other is entering a coating cavity 120 mounted in theblock 124. In FIG. 15, the mandrels 98 are fully withdrawn from thecavities on the stationary side. The preform molding cavity 114 hascooling circulation which is separate from the cooling circulation forthe preform coating cavity 120, which comprises the other mold section148. The two mandrels 98 are cooled by a single system which links allthe mandrels together. The arrow in FIG. 15 shows the rotation of theturntable 130. The turntable 130 could also rotate clockwise. Not shownare coated and uncoated preforms which would be on the mandrels if themachine were in operation. The alignment pegs and receptacles have alsobeen left out for the sake of clarity.

The operation of the overmolding apparatus will be discussed in terms ofthe preferred two mold section apparatus for making a two-layer preform.The mold is closed by moving the movable half 142 towards the stationaryhalf 144 until they are in contact. A first injection apparatus injectsa melt of first material into the first mold section 146, through thehot runners and into the preform molding cavities 114 via theirrespective gates to form the uncoated preforms each of which become theinner layer of a coated preform. The first material fills the voidbetween the preform molding cavities 114 and the mandrels 98.Simultaneously, a second injection apparatus injects a melt of secondmaterial into the second mold section 148 of the stationary half 144,through the hot runners and into each preform coating cavity 120 viatheir respective gates, such that the second material fills the void(100 in FIG. 9) between the wall of the coating cavity 120 and theuncoated preform mounted on the mandrel 98 therein.

During this entire process, cooling fluid is circulating through thethree separate areas, corresponding to the mold section 146 of thepreform molding cavities 114, mold section 148 of the preform coatingcavities 120, and the movable half 142 of the mold, respectively. Thus,the melts and preforms are being cooled in the center by the circulationin the movable half that goes through the interior of the mandrels, aswell as on the outside by the circulation in each of the cavities. Theoperating parameters of the cooling fluid in the first mold section 146containing preform molding cavities 114 are separately controlled fromthe operating parameters of the cooling fluid in the second mold section148 containing the coating cavities to account for the differentmaterial characteristics of the preform and the coating. These are inturn separate from those of the movable half of 142 the mold whichprovides constant cooling for the interior of the preform throughout thecycle, whether the mold is open or closed.

The movable half 142 then slides back to separate the two mold halvesand open the mold until all of the mandrels 98 having preforms thereonare completely withdrawn from the preform molding cavities 114 andpreform coating cavities 120. The ejectors eject the coated, finishedpreforms off of the mandrels 98 which were just removed from the preformcoating cavities. As discussed above, the ejection may cause thepreforms to completely separate from the mandrels and fall into a bin oronto a conveyor, or if the preforms remain on the mandrels afterejection, a robotic arm or other apparatus may grasp a preform or groupof preforms for removal to a bin, conveyor, or other desired location.The turntable 130 then rotates 180° so that each mandrel 98 having anuncoated preform thereon is positioned over a preform coating cavity120, and each mandrel from which a coated preform was just ejected ispositioned over a preform molding cavity 114. Rotation of the turntable130 may occur as quickly as 0.3 seconds. Using the alignment pegs 110,the mold halves again align and close, and the first injector injectsthe first material into the preform molding cavity 114 while the secondinjector injects the barrier material into the preform coating cavity120.

A production cycle of closing the mold, injecting the melts, opening themold, ejecting finished barrier preforms, rotating the turntable, andclosing the mold is repeated, so that preforms are continuously beingmolded and overmolded.

When the apparatus first begins running, during the initial cycle, nopreforms are yet in the preform coating cavities 120. Therefore, theoperator should either prevent the second injector from injecting thesecond material into the second mold section during the first injection,or allow the second material to be injected and eject and then discardthe resulting single layer preform comprised solely of the secondmaterial. After this start-up step, the operator may either manuallycontrol the operations or program the desired parameters such that theprocess is automatically controlled.

Two layer preforms may be made using the first preferred overmoldingapparatus described above. In one preferred embodiment, the two layerpreform comprises an inner layer comprising polyester and an outer layercomprising barrier material. In especially preferred embodiments, theinner layer comprises virgin PET. The description hereunder is directedtoward the especially preferred embodiments of two layer preformscomprising an inner layer of virgin PET. The description is directedtoward describing the formation of a single set of coated preforms 60 ofthe type seen in FIG. 4, that is, following a set of preforms throughthe process of molding, overmolding and ejection, rather than describingthe operation of the apparatus as a whole. The process described isdirected toward preforms having a total thickness in the wall portion 66of about 3 mm, comprising about 2 mm of virgin PET and about 1 mm ofbarrier material. The thickness of the two layers will vary in otherportions of the preform 60, as shown in FIG. 4.

It will be apparent to one skilled in the art that some of theparameters detailed below will differ if other embodiments of preformsare used. For example, the amount of time which the mold stays closedwill vary depending upon the wall thickness of the preforms. However,given the disclosure below for this preferred embodiment and theremainder of the disclosure herein, one skilled in the art would be ableto determine appropriate parameters for other preform embodiments.

The apparatus described above is set up so that the injector supplyingthe mold section 146 containing the preform molding cavities 114 is fedwith virgin PET and that the injector supplying the mold section 148containing the preform coating cavities 120 is fed with a barriermaterial. Both mold halves are cooled by circulating fluid, preferablywater, at a temperature of preferably 0-30° C., more preferably 10-15°C.

The movable half 142 of the mold is moved so that the mold is closed. Amelt of virgin PET is injected through the back of the block 124 andinto each preform molding cavity 114 to form an uncoated preform 30which becomes the inner layer of the coated preform. The injectiontemperature of the PET melt is preferably 250 to 320° C., morepreferably 255 to 280° C. The mold is kept closed for preferably 3 to 10seconds, more preferably 4 to 6 seconds while the PET melt stream isinjected and then cooled by the coolant circulating in the mold. Duringthis time, surfaces of the preforms which are in contact with surfacesof preform molding cavities 114 or mandrels 98 begin to form a skinwhile the cores of the preforms remain molten and unsolidified.

The movable half 142 of the mold is then moved so that the two halves ofthe mold are separated at or past the point where the newly moldedpreforms, which remain on the mandrels 98, are clear of the stationaryside 144 of the mold. The interior of the preforms, in contact with themandrel 98, continues to cool. The cooling is preferably done in amanner which rapidly removes heat so that crystallization of the PET isminimized so that the PET will be in a semi-crystalline state. Thechilled water circulating through the mold, as described above, shouldbe sufficient to accomplish this task.

While the inside of the preform is cooling, the temperature of theexterior surface of the preform begins to rise as it absorbs heat fromthe molten core of the preform. This heating begins to soften the skinon the exterior surface of the newly molded preform. Although the skin,which had been cooled while in the mold cavity 114, increases intemperature and begins to soften when removed from the cavity, thissoftening of the skin is the result of significant heat absorption fromthe molten core. Thus, the initial formation and later softening of theskin speeds the overall cooling of the molten preform and helps avoidcrystallization during cooling.

When the mandrels 98 are clear of the stationary side 144 of the mold,the turntable 130 then rotates 180° so that each mandrel 98 having amolded preform thereon is positioned over a preform coating cavity 120.Thus positioned, each of the other mandrels 98 which do not have moldedpreforms thereon, are each positioned over a preform molding cavity 114.The mold is again closed. Preferably the time between removal from thepreform molding cavity 114 to insertion into the preform coating cavity120 is 1 to 10 seconds, and more preferably 1 to 3 seconds.

When the molded preforms are first placed into preform coating cavities120, the exterior surfaces of the preforms are not in contact with amold surface. Thus, the exterior skin is still softened and hot asdescribed above because the contact cooling is only from the mandrelinside. The high temperature of the exterior surface of the uncoatedpreform (which forms the inner layer of the coated preform) aids inpromoting adhesion between the PET and barrier layers in the finishedbarrier coated preform. It is postulated that the surfaces of thematerials are more reactive when hot, and thus chemical interactionsbetween the barrier material and the virgin PET will be enhanced by thehigh temperatures. Barrier material will coat and adhere to a preformwith a cold surface, and thus the operation may be performed using acold initial uncoated preform, but the adhesion is markedly better whenthe overmolding process is done at an elevated temperature, as occursimmediately following the molding of the uncoated preform.

A second injection operation then follows in which a melt of a barriermaterial, is injected into each preform coating cavity 120 to coat thepreforms. The temperature of the melt of barrier material is preferably160 to 300° C. The exact temperature range for any individual barriermaterial is dependent upon the specific characteristics of that barriermaterial, but it is well within the abilities of one skilled in the artto determine a suitable range by routine experimentation given thedisclosure herein. For example, if the PHAE barrier material XU19040.00Lis used, the temperature of the melt (inject temperature) is preferably160 to 260° C., more preferably 200 to 240° C., and most preferably 220to 230° C. If the Copolyester Barrier Material B-010 is used, theinjection temperature is preferably 160 to 260° C., more preferably 190to 250° C. During the same time that this set of preforms are beingovermolded with barrier material in the preform coating cavities 120,another set of uncoated preforms is being molded in the preform moldingcavities 114 as described above.

The two halves of the mold are again separated preferably 3 to 10seconds, more preferably 4 to 6 seconds following the initiation of theinjection step. The preforms which have just been barrier coated in thepreform coating cavities 120, are ejected from the mandrels 98. Theuncoated preforms which were just molded in preform molding cavities 114remain on their mandrels 98. The turntable 130 is then rotated 180° sothat each mandrel having an uncoated preform thereon is positioned overa coating cavity 120 and each mandrel 98 from which a coated preform wasjust removed is positioned over a molding cavity 114.

The cycle of closing the mold, injecting the materials, opening themold, ejecting finished barrier preforms, rotating the turntable, andclosing the mold is repeated, so that preforms are continuously beingmolded and overmolded. Those of skill in the art will appreciate thatdry cycle time of the apparatus may increase the overall productioncycle time for molding a complete preform.

One of the many advantages of using the process disclosed herein is thatthe cycle times for the process are similar to those for the standardprocess to produce uncoated preforms; that is the molding and coating ofpreforms by this process is done in a period of time similar to thatrequired to make uncoated PET preforms of similar size by standardmethods currently used in preform production. Therefore, one can makebarrier coated PET preforms instead of uncoated PET preforms without asignificant change in production output and capacity.

If a PET melt cools slowly, the PET will take on a crystalline form.Because crystalline polymers do not blow mold as well as amorphouspolymers, a preform of crystalline PET would not be expected to performas well in forming containers according to the present invention. If,however, the PET is cooled at a rate faster than the crystal formationrate, as is described herein, crystallization will be minimized and thePET will take on a semi-crystalline form. The amorphous form is idealfor blow molding. Thus, sufficient cooling of the PET is crucial toforming preforms which will perform as needed when processed.

The rate at which a layer of PET cools in a mold such as describedherein is proportional to the thickness of the layer of PET, as well asthe temperature of the cooling surfaces with which it is in contact. Ifthe mold temperature factor is held constant, a thick layer of PET coolsmore slowly than a thin layer. This is because it takes a longer periodof time for heat to transfer from the inner portion of a thick PET layerto the outer surface of the PET which is in contact with the coolingsurfaces of the mold than it would for a thinner layer of PET because ofthe greater distance the heat must travel in the thicker layer. Thus, apreform having a thicker layer of PET needs to be in contact with thecooling surfaces of the mold for a longer time than does a preformhaving a thinner layer of PET. In other words, with all things beingequal, it takes longer to mold a preform having a thick wall of PET thanit takes to mold a preform having a thin wall of PET.

The uncoated preforms of this invention, including those made by thefirst injection in the above-described apparatus, are preferably thinnerthan a conventional PET preform for a given container size. This isbecause in making the barrier coated preforms, a quantity of the PETwhich would be in a conventional PET preform can be displaced by asimilar quantity of one of the preferred barrier materials. This can bedone because the preferred barrier materials have physical propertiessimilar to PET, as described above. Thus, when the barrier materialsdisplace an approximately equal quantity of PET in the walls of apreform or container, there will not be a significant difference in thephysical performance of the container. Because the preferred uncoatedpreforms which form the inner layer of the barrier coated preforms arethin-walled, they can be removed from the mold sooner than theirthicker-walled conventional counterparts. For example, the uncoatedpreform can be removed from the mold preferably after about 4-6 secondswithout crystallizing, as compared to about 12-24 seconds for aconventional PET preform having a total wall thickness of about 3 mm.All in all, the time to make a barrier coated preform is equal to orslightly greater (up to about 30%) than the time required to make amonolayer PET preform of this same total thickness.

Additionally, because the preferred barrier materials are amorphous,they will not require the same type of treatment as the PET. Thus, thecycle time for a molding-overmolding process as described above isgenerally dictated by the cooling time required by the PET. In theabove-described method, barrier coated preforms can be made in about thesame time it takes to produce an uncoated conventional preform.

The advantage gained by a thinner preform can be taken a step farther ifa preform made in the process is of the type in FIG. 4. In thisembodiment of a coated preform, the PET wall thickness at 70 in thecenter of the area of the end cap 42 is reduced to preferably about ⅓ ofthe total wall thickness. Moving from the center of the end cap out tothe end of the radius of the end cap, the thickness gradually increasesto preferably about ⅔ of the total wall thickness, as at referencenumber 68 in the wall portion 66. The wall thickness may remain constantor it may, as depicted in FIG. 4, transition to a lower thickness priorto the support ring 38. The thickness of the various portions of thepreform may be varied, but in all cases, the PET and barrier layer wallthicknesses must remain above critical melt flow thickness for any givenpreform design.

Using preforms 60 of the design in FIG. 4 allows for even faster cycletimes than that used to produce preforms 50 of the type in FIG. 3. Asmentioned above, one of the biggest barriers to short cycle time is thelength of time that the PET needs to be cooled in the mold followinginjection. If a preform comprising PET has not sufficiently cooledbefore it is ejected from the mandrel, it will become substantiallycrystalline and potentially cause difficulties during blow molding.Furthermore, if the PET layer has not cooled enough before theovermolding process takes place, the force of the barrier materialentering the mold will wash away some of the PET near the gate area. Thepreform design in FIG. 4 takes care of both problems by making the PETlayer thinnest in the center of the end cap region 42, which is wherethe gate is in the mold. The thin gate section allows the gate area tocool more rapidly, so that the uncoated PET layer may be removed fromthe mold in a relatively short period of time while still avoidingcrystallization of the gate and washing of the PET during the secondinjection or overmolding phase.

The physical characteristics of the preferred barrier materials help tomake this type of preform design workable. Because of the similarity inphysical properties, containers having wall portions which are primarilybarrier material can be made without sacrificing the performance of thecontainer. If the barrier material used were not similar to PET, acontainer having a variable wall composition as in FIG. 4 would likelyhave weak spots or other defects that could affect containerperformance.

2. Second Preferred Method and Apparatus for Overmolding

A second preferred apparatus 150 for performing the overmolding processis specially suited to accommodate the properties of the preform's PETinner layer and barrier material outer layer. As discussed above, thebarrier material is generally amorphous and will cool to asemi-crystalline state regardless of the cooling rate. However, PET willcool to be substantially crystalline unless it is cooled very quickly.If, however, the PET is cooled quickly, crystallization will beminimized and the PET will be mostly amorphous and well suited for blowmolding. Since the inner layer of the preferred preform is formed of PETand the outer layer is formed of a barrier material, it is mostimportant to quickly cool the preform's inner layer in order to avoidcrystallization of the PET. Thus, this second preferred apparatusretains the completed preform on a cooling mandrel 98 for a time afterremoval from the mold coating cavity 158. Thus, the mandrel 98 continuesto extract heat from the inner layer of the preform while the preformmold cavities 156, 158 are available to form other preforms.

FIG. 17 shows the second embodiment of an apparatus 150 for overmolding.Hoppers 176, 178 feed injection machines 152, 154 which heat the PET andbarrier materials and provide melt streams injected into the preformmolding cavity 156 and coating cavity 158, respectively. As in the firstpreferred embodiment discussed above, the mold is divided into astationary half 180 and a moveable half 182. The stationary half 180 hasat least two mold cavity sections 184, 186, each comprising at least oneidentical mold cavity. The first stationary mold section 184 has atleast one preform molding cavity 156 formed therein and the secondstationary mold section 186 has at least one preform coating cavity 158formed therein.

The mold of the present embodiment also has other aspects alreadydiscussed above. For instance, the mold cooling system has cooling tubeswith input and output ports for continuously circulating chilled coolantthrough the mold members; hot runners communicate molten plastic from aninjection apparatus into a void space between a mated mandrel and moldcavity to form a preform layer; the mold halves are constructed of hardmetal; and alignment pegs and corresponding receptacles aid alignment ofthe moveable half into the stationary half. Certain of these moldingcomponents are commercially available from Husky Injection MoldingSystems, Ltd.

With next reference to FIG. 18, the movable half 182 of the moldcomprises a turntable 160 divided into preferably four stations (A, B,C, D), each separated by 90° of rotation. In the illustrated embodiment,each station has a single mandrel 98 affixed thereto which correspondsto the single cavity formed in each stationary section 180. However, asin the first preferred embodiment discussed above, the number ofmandrels per station can be adjusted to increase the output of themachine so long as the number of cavities in each mold section isincreased correspondingly. Accordingly, although the illustratedembodiment shows only one mandrel per station, which would produce onlyone preform per station each production cycle, the apparatus could have,for example, three, eight, or even forty-eight mandrels per station andcavities per mold section.

Although all of the mandrels 98 are substantially identical, they willbe described and labeled herein as relating to the respective station onwhich they are located. Thus, the mandrel 98 disposed on station A islabeled 98A, the mandrel disposed on station B is labeled 98B, and soon. As above, the mandrels 98A-D serve as the mold form for the interiorof the preform. They also serve as a carrier and cooling system for thepreform during the molding operation.

The present apparatus 150 is designed to use approximately the sameinjection times, materials and temperatures discussed above. However,the orientation of the apparatus and the molds upon the turntable 160are adapted to optimize both cooling of the preforms and output by theapparatus. A preferred method of using this apparatus to overmold a twolayer preform, especially a two layer preform having a barrier materialformed as the outer layer, is described below. To illustrate theoperation of this apparatus, molding of a preform will be described byfollowing station A through a complete production cycle. It will beappreciated that stations B-D also produce preforms concurrently withstation A. FIG. 19 is a chart showing the relative activities of each ofthe stations at each point of the production cycle.

At the start of a cycle, the mandrel 96A on station A is unencumberedand directly aligned with the preform molding cavity 156 of the firstsection 184 of the stationary mold 182. An actuator 162, preferablyhydraulic, lifts the turntable 130 so that the mandrel 98A is insertedinto the molding cavity 156. The void space between the mandrel 98A andthe cavity 156 is then filled with a PET melt and allowed to cool in themold for a short time, allowing the molded preform to develop thecooling skin discussed previously. The turntable 130 is then lowered,thus pulling the mandrel 98A out of the molding cavity 156. Thejust-injected preform remains on the mandrel 98A. Once the mandrels 98are cleared of the cavities, the turntable 130 is rotated 90° so thatthe mandrel 98A is directly aligned with the coating cavity 158 of thesecond stationary mold section 186. The rotary table 130 is againlifted, inserting the mandrel 98A and the associated preform into thecoating cavity 158. A melt of barrier material is injected to coat thepreform and is allowed to cool briefly. The table 130 is again loweredand the completely-injected molded preform remains on the mandrel 98A.The turntable is rotated 90°, however the mandrel 98A is no longeraligned with any mold cavity. Instead, the mandrel 98A is left in theopen and the cooling system within the mandrel 96A continues to cool thepreform quickly from the inner surface. Alternatively, the mandrel 98Amay also be aligned with a cooling system 163 having, for example, airor water cooling tubes 165 adapted to receive the mandrel 98A andaccompanying preform, cooling the preform from the outer surface.Meanwhile, mandrels 98B and 98C of stations B and C are interacting withthe coating and molding cavities 156, 158, respectively. When theinjections are complete, the turntable again rotates 90°. Again, themandrel 98A is not aligned with any mold cavity and the cooling processcontinues. Mandrels 98C and 98D of stations C and D are at this timeinteracting with the coating and molding cavities 156, 158,respectively. The cooling preform is next ejected from the mandrel 98Aby an ejector and is removed by a device such as a robot. The robot willdeposit the completed preform on a conveyor, bin or the like. With thepreform now ejected, the mandrel 98A is again unencumbered. Oncestations C and D have completed their interactions with the moldcavities, the turntable again rotates 90° and station A and mandrel 98Aare again aligned with the preform molding cavity 156. The cycle thusstarts over again.

The above apparatus 150 may be adapted to create an apparatus 170 withimproved versatility. With next reference to FIGS. 20 and 21, instead ofthe entire turntable 130 being raised and lowered by a single hydraulicactuator, each station of the turntable 130 could be connected to itsown dedicated actuator 172. Thus, each of the stations can functionindependently to allow process optimization for the overmoldingoperation. For instance, depending on the material injected, it may bepreferable to cool the newly injected material in one cavity for alonger or shorter time than material injected into another cavity.Dedicated hydraulic actuators 172 allow the stations to be independentlymoved into and out of engagement with the respective mold cavity 156,158.

Although the above-described apparatus has been discussed in the contextof forming a two-layer preform, it will be appreciated that thedisclosed principles of construction and operation may be adapted tomold preforms having numerous layers. For instance, additional stationscould be disposed on the turntable and additional injection machines andassociated coating cavities arranged on the machine to provide forinjections of additional layers.

3. Third Preferred Method and Apparatus for Overmolding.

FIGS. 22-24 illustrate a third preferred method and apparatus 250 forovermolding which uses the principle of retaining newly-injectedpreforms on the core to hasten cooling of the inner layer of thepreforms. While the preforms are thus cooling, other mandrels interactwith mold cavities to form further preforms. The cooled preform isejected from the mandrel on which it was formed just before the mandrelis reused to mold yet another preform.

The apparatus 250 includes a stationary first mold cavity 256 connectedby hot runners to an injection apparatus 252 which supplies a PET melt.A second injection apparatus 254 is adapted to supply a melt stream of abarrier material and is vertically and stationarily oriented adjacentthe first cavity. A turntable 260 is mounted on a support member 264slidably disposed on ways 266, allowing the turntable 260 and all partsassociated therewith to travel horizontally back and forth on the ways266. The turntable 260 is rotatable through a vertical plane. Along theperipheral edges of the turntable are stations (AA, BB, CC, DD) similarto those discussed above. Mandrels 98AA-98DD are disposed on stationsAA-DD, respectively. A second mold cavity 258 is disposed above theturntable 260 and is connected thereto. The mold cavity 258 is movableby actuators 268 such as hydraulic cylinders or the like into and out ofengagement with a mandrel 98 disposed on the associated station. Thesecond mold cavity 258 also moves horizontally with the turntableapparatus. The turntable stations and the mold cavities each havecooling systems, hot runner systems, alignment systems, and the like asdiscussed above.

FIG. 22 shows the present apparatus 250 in an open position with none ofthe molds engaged. FIG. 23 shows the apparatus 250 in a closed positionwith the mandrels engaged with the respective cavities. Also, FIG. 23shows the second mold cavity 258 in position to receive a melt streamfrom the second injection apparatus 254. To move from the open positionto the closed position, the second mold cavity 258 is first drawntowards the turntable 260 and into engagement with the correspondingmandrel 98. The turntable assembly then moves horizontally along theways to engage the first cavity 256 with the corresponding mandrel 98.When the engagement is complete, the second mold cavity 258 is incommunication with the second melt source 254.

A method of forming a two layer overmolded preform is described below.As above, however, a particular mandrel 98AA will be followed through aproduction cycle. It will be appreciated that the other mandrels 98BB-DDare in concurrent use in other steps of the cycle. FIG. 24 includes achart showing the stages each station and mandrel will complete whenforming a preform using this apparatus and showing the relativepositions of each station during the production cycle.

At the beginning of a cycle, the apparatus is in the open position andthe mandrel 98AA is unencumbered by any preform. It is oriented so thatit extends horizontally and is aligned with the first mold cavity 256.Concurrently, mandrel 98DD, which has a single layer PET preform alreadydisposed thereon, is oriented vertically and is aligned with the secondmold cavity 258. To close the molds, the second mold cavity 258 is firstdrawn into engagement with the mandrel 98DD and the turntable assemblyis moved horizontally along the ways 266 so that the mandrel 98AAengages the first mold cavity 256 and the second injector 254 is broughtinto communication with the second mold cavity 258. The first injector252 then injects a melt stream of PET into the first mold cavity 256 tofill the void space between the mandrel 98AA and the first mold cavity256. Concurrently, the second injector 254 injects a melt stream ofbarrier material into the void space between the second mold cavity 258and the PET layer disposed on the mandrel 98DD. After a brief coolingtime during which a skin is formed on the just-injected PET preform, theturntable 260 is moved horizontally along the ways to pull the mandrel98AA out of engagement with the first cavity 256. As above, thejust-injected preform remains on the mandrel 98AA. The second moldcavity 258 is then withdrawn from the mandrel 98DD and the rotatingturntable 260 is rotated 90° so that mandrel 98AA is now aligned withthe second mold cavity 258 and the mandrel 98BB is now aligned with thefirst mold cavity 256. The mold is closed as above and a layer ofbarrier material is injected onto the PET preform on mandrel 98AA whilea PET preform is formed on mandrel 98BB. After a brief cooling time, themold is again opened as above and the turntable 260 is rotated 90°.Mandrel 98AA is now free of any mold cavities and the newly moldedpreform disposed on the mandrel 98AA is cooled during this time.Concurrently, mandrels 98BB and 98CC are in communication with the moldcavities. After the injections involving mandrels 98BB and 98CC arecomplete, the rotating table 260 is again rotated 90°. The mandrel 98AAis again retained in a cooling position out of alignment with any moldcavity. Concurrently, mandrels 98CC and 98DD engage the mold cavitiesand have layers injected thereon. The now-cooled preform is ejected fromthe mandrel 98AA to a conveyor or bin below the turntable 260 and theturntable 260 is again rotated 90°. Mandrel 98AA is again unencumbered,aligned with the first mold cavity 258, and ready to begin anotherproduction cycle.

Although the above-described apparatus 250 has been discussed in thecontext of forming a two-layer preform, it will be appreciated that thedisclosed principles of construction and operation may be adapted tomold preforms having numerous layers. For instance, additional stationscould be disposed on the turntable and additional injection machines andassociated coating cavities arranged on the machine to provide forinjections of additional layers.

4. Lamellar Injection Molding

A barrier layer or a barrier preform can also be produced by a processcalled lamellar injection molding (LIM). The essence of LIM processes isthe creation of a meltstream which is composed of a plurality of thinlayers. In this application, it is preferred that the LIM meltstream iscomprised of alternating thin layers of PET and barrier material. TheLIM process may be used in conjunction with the above-describedpreferred overmolding apparatus to overmold a coating of multiple, thinlayers.

One method of lamellar injection molding is carried out using a systemsimilar to that disclosed in several patents to Schrenk, U.S. Pat. Nos.5,202,074, 5,540,878, and 5,628,950, the disclosures of which are herebyincorporated in their entireties by reference, although the use of thatmethod as well as other methods obtaining similar lamellar meltstreamsare contemplated as part of the present invention. Referring to FIG. 25,a schematic of a LIM system 270 is shown. The system in FIG. 25 shows atwo material system, but it will be understood that a system for threeor more materials could be used in a similar fashion. The two materialswhich are to form the layers, at least one of which is preferably abarrier resin, are placed in separate hoppers 272 and 274, which feedtwo separate cylinders, 276 and 278 respectively. The materials arecoextruded at rates designed to provide the desired relative amounts ofeach material to form a lamellar meltstream comprised of a layer fromeach cylinder.

The lamellar meltstream output from combined cylinders is then appliedto a layer generation system 280. In the layer generation system 280,the two layer meltstream is multiplied into a multi-layer meltstream byrepetition of a series of actions much like one would do to make apastry dough having a number of layers. First, one divides a section ofmeltstream into two pieces perpendicular to the interface of the twolayers. Then the two pieces are flattened so that each of the two piecesis about as long as the original section before it was halved in thefirst step, but only half as thick as the original section. Then the twopieces are recombined into one piece having similar dimensions as theoriginal section, but having four layers, by stacking one piece on topof the other piece so that the sublayers of the two materials areparallel to each other. These three steps of dividing, flattening, andrecombining the meltstream may be done several times to create morethinner layers. The meltstream may be multiplied by performing thedividing, flattening and recombining a number of times to produce asingle melt stream consisting of a plurality of sublayers of thecomponent materials. In this two material embodiment, the composition ofthe layers will alternate between the two materials. The output from thelayer generation system passes through a neck 282 and is injected into amold to form a preform or a coating.

A system such as that in FIG. 25 to generate a lamellar meltstream maybe used in place of one or both of the injectors in the overmoldingprocess and apparatus described above. Alternatively, a barrier preformcould be formed using a single injection of a LIM meltstream if themeltstream comprised barrier material. If a preform is made exclusivelyfrom a LIM meltstream or is made having an inner layer which was madefrom a LIM meltstream, and the container made therefrom is to be incontact with edibles, it is preferred that all materials in the LIMmeltstream have FDA approval.

In one preferred embodiment, a preform of the type in FIG. 4 is madeusing an inject-over-inject process wherein a lamellar meltstream isinjected into the barrier coating cavities. Such a process, in which apreform is overmolded with a lamellar meltstream, can be calledLIM-over-inject. In a LIM-over-inject process to create a preform fromwhich a beverage bottle is made by blow molding, the first or innerlayer 72 is preferably virgin PET, and the LIM meltstream is preferablya barrier material, such as PHAE, and recycled PET. Recycled PET is usedin the outer layer 74 because it will not be in contact with edibles andit is cheaper to use to make up the bulk of a container than is virginPET or most barrier materials.

FIG. 4A shows an enlarged view of a wall section 3 of a preform of thetype in FIG. 4 made by a LIM over inject process. The inner layer 72 isa single material, but the outer layer 74 is comprised of a plurality ofmicrolayers formed by the LIM process.

An exemplary process to make such a preform is as follows. Recycledpolyethylene terephthalate is applied through a feed hopper 272 to afirst cylinder 276, while simultaneously, a barrier material is appliedthrough a second feed hopper 274 to a second cylinder 278. The twomaterials are coextruded at rates to provide two-layer lamellarmeltstream comprising preferably 60-95 wt. % recycled polyethyleneterephthalate and preferably 5-40 wt. % barrier material. The lamellarmeltstream is applied to the layer generation system 280 in which alamellar melt stream comprising the two materials is formed by dividing,flattening and recombining the meltstream, preferably at least twice.This lamellar melt stream exits at 282 and is then injected into a mold,such as that depicted in FIG. 9. Preferably, the lamellar melt stream isinjected into the preform coating cavities 120 of in an overmoldingapparatus such as that in FIGS. 10 and 11 over a preform, to form aLIM-over-inject coated preform comprising a barrier layer consisting ofalternating microlayers of barrier material and recycled PET.

In another exemplary process, virgin PET is applied through a feedhopper 272 to a first cylinder 276, while simultaneously, B-010 isapplied through a second feed hopper 274 to a second cylinder 278. Thetwo polymers are coextruded at rates to provide a meltstream comprisingpreferably 60-95 wt. % virgin polyethylene terephthalate and preferably5-40 wt. % B-010. The two layer meltstream is applied to a layergeneration system 280 in which a lamellar melt stream comprising the twomaterials is formed by dividing flattening and recombining themeltstream, preferably at least twice. This lamellar melt stream exitsat 282 and is then injected into the preform molding cavities 156, 256of any of the overmolding apparatus 150, 250 described above. Thisinitial LIM preform is overinjected with recycled PET in the preformcoating cavities 158, 258 to produce a preform with an inner layerconsisting of alternating microlayers of barrier material and virginPET, and an outer layer of recycled PET. Such a process may be calledinject-over-LIM.

In the multilayer preform, LIM-over-inject or inject-over-LIMembodiments, the lamellar injection system can be used to advantage toprovide a plurality of alternating and repeating sublayers, preferablycomprised of PET and a barrier material. The multiple layers of theseembodiments of the invention offers a further safeguard againstpremature diffusion of gases through the sidewall of the beveragecontainer or other food product container.

H. Improving Mold Performance

As discussed above, the mold halves have an extensive cooling systemcomprising circulating coolant throughout the mold in order to conductheat away and thus enhance the mold's heat absorption properties. Withnext reference to FIG. 26, which is a cross-section of a mold mandrel298 and cavity 300 having features in accordance with the presentinvention, the mold cooling system can be optimized for the moldcavities by arranging cooling tubes 302 in a spiral around the moldcavity 300 and just below the surface 304. The rapid cooling enabled bysuch a cooling system helps avoid crystallization of the PET layerduring cooling. Also, the rapid cooling decreases the production cycletime by allowing injected preforms to be removed from the mold cavitiesquickly so that the mold cavity 300 may be promptly reused.

As discussed above, the gate area 306 of the mold cavity 300 isespecially pivotal in determining cycle time. The void space near thegate 308, which will make up the molded preform's base end 304, receivesthe last portion of the melt stream to be injected into the mold cavity300. Thus, this portion is the last to begin cooling. If the PET layerhas not sufficiently cooled before the overmolding process takes place,the force of the barrier material melt entering the mold may wash awaysome of the PET near the gate area 308. To speed cooling in the gatearea of the mold cavity in order to decrease cycle time, inserts 310 ofan especially high heat transfer material such as Ampcoloy can bedisposed in the mold in the gate area 308. These Ampcoloy inserts 310will withdraw heat at an especially fast rate. To enhance and protectthe Ampcoloy inserts 310, a thin layer of titanium nitride or hardchrome may be deposited on the surface 312 of the Ampcoloy to form ahard surface. Such a deposited surface would be preferably between only0.001 and 0.01 inches thick and would most preferably be about 0.002inches thick.

As discussed above, the mandrel 298 is especially important in thecooling process because it directly cools the inner PET layer. Toenhance the cooling effect of the mandrel 298 on the inner surface ofthe preform and especially to enhance the cooling effect of the mandrel298 at the preform's gate area/base end 314, the mandrel 298 ispreferably substantially hollow, having a relatively thin uniform wall320, as shown in FIG. 26. Preferably, this uniform thickness is between0.1 inch and 0.3 inches and is most preferably about 0.2 inches. It isparticularly important that the wall 320 at the base end 322 of themandrel 298 is no thicker than the rest of the mandrel wall 314 becausethe thin wall aids in rapidly communicating heat away from the moltengate area 314 of the injected preform.

To further enhance the mandrel's cooling capability, cooling water maybe supplied in a bubbler arrangement 330. A core tube 332 is disposedcentrally in the mandrel 298 and delivers chilled coolant C to the baseend 322 thereof. Since the base end 322 is the first point of themandrel 298 contacted by this coolant C, the coolant is coldest and mosteffective at this location. Thus, the gate area 314 of the injectedpreform is cooled at a faster rate than the rest of the preform. Coolantinjected into the mandrel at the base end 322 proceeds along the lengthof the mandrel 298 and exits through an output line 334. A plurality ofribs 336 are arranged in a spiral pattern around the core 332 to directcoolant C along the mandrel wall.

Another way to enhance cooling of the preform's gate area was discussedabove and involves forming the mold cavity so that the inner PET layeris thinner at the gate area than at the rest of the injected preform asshown in FIG. 4. The thin gate area thus cools quickly to asubstantially solid state and can be quickly removed from the first moldcavity, inserted into the second mold cavity, and have a layer ofbarrier material injected thereover without causing washing of the PET.

In the continuing effort to reduce cycle time, injected preforms areremoved from mold cavities as quickly as possible. However, it may beappreciated that the newly injected material is not necessarily fullysolidified when the injected preform is removed from the mold cavity.This results in possible problems removing the preform from the cavity300. Friction or even a vacuum between the hot, malleable plastic andthe mold cavity surface 304 can cause resistance resulting in damage tothe injected preform when an attempt is made to remove it from the moldcavity 300.

Typically, mold surfaces are polished and extremely smooth in order toobtain a smooth surface of the injected part. However, polished surfacestend to create surface tension along those surfaces. This surfacetension may create friction between the mold and the injected preformwhich may result in possible damage to the injected preform duringremoval from the mold. To reduce surface tension, the mold surfaces arepreferably treated with a very fine sanding device to slightly roughenthe surface of the mold. Preferably the sandpaper has a grit ratingbetween about 400 and 700. More preferably a 600 grit sandpaper is used.Also, the mold is preferably sanded in only a longitudinal direction,further facilitating removal of the injected preform from the mold.

During injection, air is pushed out of the mold cavity 300 by theinjected meltstream. As a result, a vacuum may develop between theinjected preform and the mold cavity wall 304. When the injected preformis removed from the cavity 300, the vacuum may resist removal, resultingin damage to the not-fully-solidified preform. To defeat the vacuum, anair insertion system 340 may be employed. With additional reference toFIGS. 27 and 28, an embodiment of an air insertion system 340 isprovided. At a joint 342 of separate members of the mold cavity 300, anotch 344 is preferably formed circumferentially around and opening intothe mold cavity 300. The notch 344 is preferably formed by a step 346 ofbetween 0.002 inches and 0.005 inches and most preferably about 0.003inches in depth. Because of its small size, the notch 344 will not fillwith plastic during injection but will enable air A to be introducedinto the mold cavity 300 to overcome the vacuum during removal of theinjected preform from the mold cavity 300. An air line 350 connects thenotch 344 to a source of air pressure and a valve (not shown) controlsthe supply of air A. During injection, the valve is closed so that themelt fills the mold cavity 300 without air resistance. When injection iscomplete, the valve opens and a supply of air is delivered to the notch344 at a pressure between about 75 psi and 150 psi and most preferablyabout 100 psi. The supply of air defeats any vacuum that may formbetween the injected preform and the mold cavity, aiding removal of thepreform. Although the drawings show only a single air supply notch 344in the mold cavity 300, any number of such notches may be provided andin a variety of shapes depending on the size and shape of the mold.

While some of the above-described improvements to mold performance arespecific to the method and apparatus described herein, those of skill inthe art will appreciate that these improvements may also be applied inmany different types of plastic injection molding applications andassociated apparatus. For instance, use of Ampcoloy in a mold mayquicken heat removal and dramatically decrease cycle times for a varietyof mold types and melt materials. Also, roughening of the moldingsurfaces and provides air pressure supply systems may ease part removalfor a variety of mold types and melt materials.

I. Formation of Preferred Containers by Blow Molding

The barrier-coated containers preferably produced by blow-molding thebarrier-coated preforms, the creation of which is disclosed above. Thebarrier-coated preforms can be blow-molded using techniques andconditions very similar, if not identical, to those by which uncoatedPET preforms are blown into containers. Such techniques and conditionsfor blow-molding monolayer PET preforms into bottles are well known tothose skilled in the art and can be used or adapted as necessary.

Generally, in such a process, the preform is heated to a temperature ofpreferably 80 to 120° C., more preferably 100 to 105° C., and given abrief period of time to equilibrate. After equilibration, it isstretched to a length approximating the length of the final container.Following the stretching, pressurized air is forced into the preformwhich acts to expand the walls of the preform to fit the mold in whichit rests, thus creating the container.

J. Testing of Laminate Bottles

Several bottles were made according to the overmolding processes of thepresent invention, having varying amounts of IPA in the PET, and usingPHAE as the barrier material. Control bottles were also made from PEThaving no IPA therein.

The test bottles were made by blow-molding preforms made by theovermolding process described above. An impact test was then performedon the bottles, whereby the sidewall (body portion) of each bottle wasstruck by an impacting force. The bottles were then observed for signsof physical damage, most importantly delamination of the laminatematerial in the sidewall of the bottle.

It was found that the bottles having inner PET layers having higherlevels of IPA experienced less delamination when subjected to the impacttest than laminates having lower levels of IPA, which still fared betterthan those bottles made from PET having no IPA at all. Thus, it is shownthat better adhesion between the layers of the laminate is achieved whenIPA-PET is used in making laminates with phenoxy materials.

Although the present invention has been described in terms of certainpreferred embodiments, and certain exemplary methods, it is to beunderstood that the scope of the invention is not to be limited thereby.Instead, Applicant intends that the scope of the invention be limitedsolely by reference to the attached claims, and that variations on themethods and materials disclosed herein which are apparent to those ofskill in the art will fall within the scope of Applicant's invention.

1. A molding assembly for injection molding a two-layer preform, the molding assembly comprising: a cavity portion; and a mandrel portion being configured to rotate, the mandrel portion being divided into four stations, each station separated by 90 degrees of rotation; wherein a first station of the mandrel portion comprises a plurality of molding mandrels and a second station of the mandrel portion comprises a plurality of coating mandrels; wherein the first and second stations of the mandrel portion are configured to simultaneously mate with corresponding cavities of the cavity portion; and wherein the molding mandrels comprise a molding mandrel cooling system and the coating mandrels comprise a coating mandrel cooling system, wherein operating parameters of the molding cooling system are configured to be separately controlled from operating parameters of the coating cooling system.
 2. The molding assembly of claim 1, wherein the cavity portion comprises at least two cavity stations, each cavity section comprising a plurality of cavities, each cavity comprising a cavity mold surface, wherein at least some of the cavities comprise a fluid insertion system.
 3. The molding assembly of claim 2, the fluid insertion system comprises a notch along the cavity mold surface.
 4. The injection molding assembly of claim 3, wherein the notch is at least partially circumferentially disposed around the cavity mold surface.
 5. The molding assembly of claim 1, wherein mandrel portion comprises a high heat transfer material. 